fix(bot,discord): allow 'no player limit' option in /newsession wizard

In the session creation wizard (Telegram + Discord), the Capacity step
only exposed waitlist on/off buttons. The 'no waitlist' button silently
advanced to the next step without setting MaxPlayers, so users who tried
to create a session with no player cap were blocked with
'Не заполнены поля: лимит мест'.

The DB contract and CreateSessionCommand already supported null
MaxPlayers (int?, ck_sessions_max_players check in V006), and the web
form already exposes 'Без лимита' as an empty InputNumber — only the
wizard flow was broken.

Changes:
- Add '♾ Без лимита' choice button to Capacity in shared
  WizardStepViewBuilder.BuildCapacity (Telegram) and to
  RenderCapacity / RenderPoolSlotCapacity in DiscordWizardStep (Discord).
- Add 'no_limit' branch to GameCreationWizard.ApplyCapacityChoice that
  sets MaxPlayers to null and advances to Visibility.
- Change GameCreationWizard.SetMaxPlayers signature from int to int? so
  the 'no limit' branch compiles.
- Change CreateSessionCommand builder in both Telegram and Discord
  submitters to take int? maxPlayers and drop the '?? 0' that would
  have turned null into 0 (violating the DB CHECK and the 'no limit'
  contract).
- In Discord BuildConfirmDescription, render '👥 Без лимита, waitlist
  вкл/выкл' when MaxPlayers is null (the previous code silently
  omitted the line).
- Expose BuildCommand as internal in both submitters and add
  InternalsVisibleTo('GmRelay.Bot.Tests') to the DiscordBot assembly
  for unit-test access.

Tests (9 new):
- WizardStepRenderTests.CapacityStep_HasWaitlistButtons — asserts the
  'Без лимита' button is present.
- GameCreationWizardStepTransitionsTests.NoLimitCapacityButton_… —
  asserts the choice advances to Visibility and leaves MaxPlayers null
  in the JSON draft.
- GameCreationWizardStepTransitionsTests.ChoiceCallback_AdvancesToExpectedStep —
  new Theory row for Capacity/no_limit.
- CreateSessionHandlerBuildCommandTests (new) — null/value propagation
  through the Telegram submitter's BuildCommand.
- DiscordWizardStepCapacityRenderTests (new) — 'Без лимита' button is
  rendered for both Capacity and PoolSlotCapacity, with the expected
  custom-id shape.
- DiscordWizardSubmitterBuildCommandTests (new) — null/value
  propagation through the Discord submitter's BuildCommand.

Closes #123

src/GmRelay.Bot/Features/Sessions/CreateSession/CreateSessionHandler.cs

@@ -170,7 +170,7 @@ public sealed class CreateSessionHandler
                 draft,
                 p,
                 new[] { p.Single?.ScheduledAt ?? default },
-                p.Single?.MaxPlayers ?? 0,
+                p.Single?.MaxPlayers,
                 isOneShot: true),
         };
     }
@@ -178,11 +178,11 @@ public sealed class CreateSessionHandler
     private static int MaxPlayersForPool(WizardPoolInput pool) =>
         pool.Slots.Count == 0 ? 0 : pool.Slots.Max(s => s.MaxPlayers);
 
-    private static CreateSessionCommand BuildCommand(
+    internal static CreateSessionCommand BuildCommand(
         WizardDraft draft,
         WizardPayload p,
         IReadOnlyList<DateTimeOffset> scheduledTimes,
-        int maxPlayers,
+        int? maxPlayers,
         bool isOneShot)
     {
         var user = new PlatformUser(

src/GmRelay.DiscordBot/Features/Sessions/Wizard/DiscordWizardStep.cs

@@ -252,11 +252,12 @@ public static class DiscordWizardStep
 
     private static DiscordWizardRender RenderCapacity() => new(
         "👥 Лимит мест",
-        "Введите лимит (1..50) и выберите waitlist.",
+        "Введите лимит (1..50), выберите waitlist или сразу «♾ Без лимита».",
         new[]
         {
             Row(ChoiceBtn("✅ Waitlist вкл", WizardStepNames.Capacity, "waitlist:on", ButtonStyle.Success),
                 ChoiceBtn("❌ Без waitlist", WizardStepNames.Capacity, "waitlist:off", ButtonStyle.Danger)),
+            Row(ChoiceBtn("♾ Без лимита", WizardStepNames.Capacity, "no_limit", ButtonStyle.Primary)),
             Row(ControlBtn("⬅️ Назад", "back"),
                 ControlBtn("❌ Отмена", "cancel", ButtonStyle.Danger)),
         },
@@ -371,11 +372,12 @@ public static class DiscordWizardStep
 
     private static DiscordWizardRender RenderPoolSlotCapacity() => new(
         "👥 Лимит слотов",
-        "Введите лимит (1..50) и выберите waitlist.",
+        "Введите лимит (1..50), выберите waitlist или сразу «♾ Без лимита».",
         new[]
         {
             Row(ChoiceBtn("✅ Waitlist вкл", WizardStepNames.PoolSlotCapacity, "waitlist:on", ButtonStyle.Success),
                 ChoiceBtn("❌ Без waitlist", WizardStepNames.PoolSlotCapacity, "waitlist:off", ButtonStyle.Danger)),
+            Row(ChoiceBtn("♾ Без лимита", WizardStepNames.PoolSlotCapacity, "no_limit", ButtonStyle.Primary)),
             Row(ControlBtn("⬅️ Назад", "back"),
                 ControlBtn("❌ Отмена", "cancel", ButtonStyle.Danger)),
         },
@@ -417,6 +419,10 @@ public static class DiscordWizardStep
         {
             sb.Append("👥 Мест: ").Append(mp).Append(", waitlist ").Append(p.Waitlist == true ? "вкл" : "выкл").AppendLine();
         }
+        else if (p.Type == WizardCreationType.Single)
+        {
+            sb.Append("👥 Без лимита, waitlist ").Append(p.Waitlist == true ? "вкл" : "выкл").AppendLine();
+        }
         sb.Append("🔒 Видимость: ").AppendLine(RenderVisibilityText(p.Visibility));
         return sb.ToString();
     }

src/GmRelay.DiscordBot/Features/Sessions/Wizard/DiscordWizardSubmitter.cs

@@ -134,7 +134,7 @@ public sealed class DiscordWizardSubmitter
                 draft,
                 p,
                 new[] { p.Single?.ScheduledAt ?? default },
-                p.Single?.MaxPlayers ?? 0,
+                p.Single?.MaxPlayers,
                 isOneShot: true),
         };
     }
@@ -142,11 +142,11 @@ public sealed class DiscordWizardSubmitter
     private static int MaxPlayersForPool(WizardPoolInput pool) =>
         pool.Slots.Count == 0 ? 0 : pool.Slots.Max(s => s.MaxPlayers);
 
-    private static CreateSessionCommand BuildCommand(
+    internal static CreateSessionCommand BuildCommand(
         WizardDraft draft,
         WizardPayload p,
         IReadOnlyList<DateTimeOffset> scheduledTimes,
-        int maxPlayers,
+        int? maxPlayers,
         bool isOneShot)
     {
         var user = new PlatformUser(

src/GmRelay.DiscordBot/Properties/AssemblyInfo.cs

@@ -0,0 +1,3 @@
+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("GmRelay.Bot.Tests")]

src/GmRelay.Shared/Features/Sessions/CreateSession/Wizard/GameCreationWizard.cs

@@ -302,6 +302,7 @@ public sealed class GameCreationWizard
     {
         "waitlist:on" => (WizardStepNames.Visibility, SetWaitlist(p, true)),
         "waitlist:off" => (WizardStepNames.Visibility, SetWaitlist(p, false)),
+        "no_limit" => (WizardStepNames.Visibility, SetMaxPlayers(p, null)),
         _ => (null, "Неизвестный выбор"),
     };
 
@@ -416,7 +417,7 @@ public sealed class GameCreationWizard
     private static string? SetDurationMinutes(WizardPayload p, int? v) { p.DurationMinutes = v; return null; }
     private static string? SetScheduledAt(WizardPayload p, DateTimeOffset v)
     { p.Single ??= new WizardSingleInput(); p.Single.ScheduledAt = v; return null; }
-    private static string? SetMaxPlayers(WizardPayload p, int v)
+    private static string? SetMaxPlayers(WizardPayload p, int? v)
     { p.Single ??= new WizardSingleInput(); p.Single.MaxPlayers = v; return null; }
     private static string? SetWaitlist(WizardPayload p, bool v) { p.Waitlist = v; return null; }
     private static string? SetVisibility(WizardPayload p, WizardVisibility? v) { p.Visibility = v; return null; }

src/GmRelay.Shared/Features/Sessions/CreateSession/Wizard/WizardStepViewBuilder.cs

@@ -97,11 +97,12 @@ public static class WizardStepViewBuilder
         BackCancel());
 
     private static (string, IReadOnlyList<WizardAction>) BuildCapacity() => (
-        "👥 Введите лимит мест (1..50) одним числом.\nЗатем нажмите кнопку waitlist.",
+        "👥 Введите лимит мест (1..50) одним числом.\nЗатем нажмите кнопку waitlist. Или сразу «♾ Без лимита».",
         new List<WizardAction>
         {
             new("✅ Waitlist вкл", WizardCallbackData.Choice(WizardStepNames.Capacity, "waitlist:on"), WizardActionStyle.Success),
             new("❌ Без waitlist", WizardCallbackData.Choice(WizardStepNames.Capacity, "waitlist:off"), WizardActionStyle.Danger),
+            new("♾ Без лимита", WizardCallbackData.Choice(WizardStepNames.Capacity, "no_limit"), WizardActionStyle.Primary),
         });
 
     private static (string, IReadOnlyList<WizardAction>) BuildVisibility() => (

tests/GmRelay.Bot.Tests/Discord/Wizard/DiscordWizardStepCapacityRenderTests.cs

@@ -0,0 +1,64 @@
+using GmRelay.DiscordBot.Features.Sessions.Wizard;
+using GmRelay.Shared.Features.Sessions.CreateSession.Wizard;
+using NetCord.Rest;
+using Xunit;
+
+namespace GmRelay.Bot.Tests.Discord.Wizard;
+
+/// <summary>
+/// Renderer tests for the Discord wizard's Capacity / PoolSlotCapacity steps.
+/// Locks in the presence of the "♾ Без лимита" button so the user can pick
+/// a session with no player cap (null in <c>sessions.max_players</c>), the
+/// same affordance the Telegram wizard provides.
+/// </summary>
+public sealed class DiscordWizardStepCapacityRenderTests
+{
+    [Fact]
+    public void RenderCapacity_ContainsNoLimitButton()
+    {
+        var draft = new WizardDraft { Step = WizardStepNames.Capacity };
+        var render = DiscordWizardStep.Render(draft, new WizardPayload());
+
+        var labels = ExtractButtonLabels(render);
+        Assert.Contains(labels, l => l.Contains("Без лимита", System.StringComparison.Ordinal));
+    }
+
+    [Fact]
+    public void RenderPoolSlotCapacity_ContainsNoLimitButton()
+    {
+        var draft = new WizardDraft { Step = WizardStepNames.PoolSlotCapacity };
+        var render = DiscordWizardStep.Render(draft, new WizardPayload());
+
+        var labels = ExtractButtonLabels(render);
+        Assert.Contains(labels, l => l.Contains("Без лимита", System.StringComparison.Ordinal));
+    }
+
+    [Fact]
+    public void RenderCapacity_NoLimitButton_HasChoiceCustomIdForNoLimit()
+    {
+        var draft = new WizardDraft { Step = WizardStepNames.Capacity };
+        var render = DiscordWizardStep.Render(draft, new WizardPayload());
+
+        var buttons = ExtractButtons(render);
+        var noLimit = buttons.SingleOrDefault(b => b.Label?.Contains("Без лимита", System.StringComparison.Ordinal) == true);
+        Assert.NotNull(noLimit);
+        Assert.StartsWith("wizard:btn:choice:Capacity:no_limit", noLimit!.CustomId);
+    }
+
+    private static System.Collections.Generic.List<string> ExtractButtonLabels(
+        DiscordWizardStep.DiscordWizardRender render) =>
+        render.Components
+            .OfType<ActionRowProperties>()
+            .SelectMany(r => r.Components)
+            .OfType<ButtonProperties>()
+            .Select(b => b.Label ?? string.Empty)
+            .ToList();
+
+    private static System.Collections.Generic.List<ButtonProperties> ExtractButtons(
+        DiscordWizardStep.DiscordWizardRender render) =>
+        render.Components
+            .OfType<ActionRowProperties>()
+            .SelectMany(r => r.Components)
+            .OfType<ButtonProperties>()
+            .ToList();
+}

tests/GmRelay.Bot.Tests/Discord/Wizard/DiscordWizardSubmitterBuildCommandTests.cs

@@ -0,0 +1,85 @@
+using GmRelay.DiscordBot.Features.Sessions.Wizard;
+using GmRelay.Shared.Features.Sessions.CreateSession.Wizard;
+using Xunit;
+
+namespace GmRelay.Bot.Tests.Discord.Wizard;
+
+/// <summary>
+/// Regression coverage for <see cref="DiscordWizardSubmitter"/>'s
+/// <c>BuildCommand</c>: when the wizard payload carries no player limit
+/// (user picked «♾ Без лимита» on the Capacity step), the resulting
+/// <c>CreateSessionCommand.MaxPlayers</c> must be <c>null</c> — never
+/// <c>0</c>. <c>0</c> would violate the DB CHECK
+/// <c>ck_sessions_max_players</c> in V006 and the contract that
+/// <c>null</c> means "no limit".
+/// </summary>
+public sealed class DiscordWizardSubmitterBuildCommandTests
+{
+    [Fact]
+    public void BuildCommand_WhenSingleMaxPlayersIsNull_PropagatesNull()
+    {
+        var draft = new WizardDraft
+        {
+            Id = Guid.NewGuid(),
+            ChatId = "42",
+            OwnerId = "100",
+            Step = "confirm",
+        };
+        var payload = new WizardPayload
+        {
+            Type = WizardCreationType.Single,
+            Title = "T",
+            System = "Dnd5e",
+            DurationMinutes = 240,
+            Visibility = WizardVisibility.Public,
+            Single = new WizardSingleInput
+            {
+                ScheduledAt = DateTimeOffset.UtcNow.AddDays(1),
+                MaxPlayers = null,
+            },
+        };
+
+        var cmd = DiscordWizardSubmitter.BuildCommand(
+            draft,
+            payload,
+            new[] { payload.Single!.ScheduledAt!.Value },
+            payload.Single.MaxPlayers,
+            isOneShot: true);
+
+        Assert.Null(cmd.MaxPlayers);
+    }
+
+    [Fact]
+    public void BuildCommand_WhenSingleMaxPlayersIsSet_PropagatesValue()
+    {
+        var draft = new WizardDraft
+        {
+            Id = Guid.NewGuid(),
+            ChatId = "42",
+            OwnerId = "100",
+            Step = "confirm",
+        };
+        var payload = new WizardPayload
+        {
+            Type = WizardCreationType.Single,
+            Title = "T",
+            System = "Dnd5e",
+            DurationMinutes = 240,
+            Visibility = WizardVisibility.Public,
+            Single = new WizardSingleInput
+            {
+                ScheduledAt = DateTimeOffset.UtcNow.AddDays(1),
+                MaxPlayers = 5,
+            },
+        };
+
+        var cmd = DiscordWizardSubmitter.BuildCommand(
+            draft,
+            payload,
+            new[] { payload.Single!.ScheduledAt!.Value },
+            payload.Single.MaxPlayers,
+            isOneShot: true);
+
+        Assert.Equal(5, cmd.MaxPlayers);
+    }
+}

tests/GmRelay.Bot.Tests/Features/Sessions/CreateSession/Wizard/CreateSessionHandlerBuildCommandTests.cs

@@ -0,0 +1,85 @@
+using GmRelay.Bot.Features.Sessions.CreateSession;
+using GmRelay.Shared.Features.Sessions.CreateSession.Wizard;
+using Xunit;
+
+namespace GmRelay.Bot.Tests.Features.Sessions.CreateSession.Wizard;
+
+/// <summary>
+/// Regression coverage for <see cref="CreateSessionHandler.BuildCommand"/>:
+/// when the wizard payload carries no player limit (e.g. user picked
+/// «♾ Без лимита» on the Capacity step), the resulting
+/// <c>CreateSessionCommand.MaxPlayers</c> must be <c>null</c> — never <c>0</c>.
+/// <c>0</c> would violate the DB CHECK constraint
+/// (<c>ck_sessions_max_players</c> in V006) by inserting <c>0</c> instead of
+/// <c>NULL</c>, which is the wire-level representation of "no limit".
+/// </summary>
+public sealed class CreateSessionHandlerBuildCommandTests
+{
+    [Fact]
+    public void BuildCommand_WhenSingleMaxPlayersIsNull_PropagatesNull()
+    {
+        var draft = new WizardDraft
+        {
+            Id = Guid.NewGuid(),
+            ChatId = "42",
+            OwnerId = "100",
+            Step = "confirm",
+        };
+        var payload = new WizardPayload
+        {
+            Type = WizardCreationType.Single,
+            Title = "T",
+            System = "Dnd5e",
+            DurationMinutes = 240,
+            Visibility = WizardVisibility.Public,
+            Single = new WizardSingleInput
+            {
+                ScheduledAt = DateTimeOffset.UtcNow.AddDays(1),
+                MaxPlayers = null,
+            },
+        };
+
+        var cmd = CreateSessionHandler.BuildCommand(
+            draft,
+            payload,
+            new[] { payload.Single!.ScheduledAt!.Value },
+            payload.Single.MaxPlayers,
+            isOneShot: true);
+
+        Assert.Null(cmd.MaxPlayers);
+    }
+
+    [Fact]
+    public void BuildCommand_WhenSingleMaxPlayersIsSet_PropagatesValue()
+    {
+        var draft = new WizardDraft
+        {
+            Id = Guid.NewGuid(),
+            ChatId = "42",
+            OwnerId = "100",
+            Step = "confirm",
+        };
+        var payload = new WizardPayload
+        {
+            Type = WizardCreationType.Single,
+            Title = "T",
+            System = "Dnd5e",
+            DurationMinutes = 240,
+            Visibility = WizardVisibility.Public,
+            Single = new WizardSingleInput
+            {
+                ScheduledAt = DateTimeOffset.UtcNow.AddDays(1),
+                MaxPlayers = 5,
+            },
+        };
+
+        var cmd = CreateSessionHandler.BuildCommand(
+            draft,
+            payload,
+            new[] { payload.Single!.ScheduledAt!.Value },
+            payload.Single.MaxPlayers,
+            isOneShot: true);
+
+        Assert.Equal(5, cmd.MaxPlayers);
+    }
+}

tests/GmRelay.Bot.Tests/Features/Sessions/CreateSession/Wizard/GameCreationWizardStepTransitionsTests.cs

@@ -23,6 +23,7 @@ public sealed class GameCreationWizardStepTransitionsTests
     // Capacity → Visibility
     [InlineData(WizardStepNames.Capacity, "waitlist:on", WizardStepNames.Visibility)]
     [InlineData(WizardStepNames.Capacity, "waitlist:off", WizardStepNames.Visibility)]
+    [InlineData(WizardStepNames.Capacity, "no_limit", WizardStepNames.Visibility)]
     // Visibility → Publish (public, no club)
     [InlineData(WizardStepNames.Visibility, "public", WizardStepNames.Publish)]
     // Visibility → PickClub
@@ -70,6 +71,32 @@ public sealed class GameCreationWizardStepTransitionsTests
         Assert.Equal(240, dur.GetInt32());
     }
 
+    [Fact]
+    public async Task NoLimitCapacityButton_AdvancesToVisibility_AndLeavesMaxPlayersNull()
+    {
+        var wizard = BuildWizard(out var drafts, out _);
+        var draft = NewDraft(WizardStepNames.Capacity, PayloadForStep(WizardStepNames.Capacity));
+        drafts.Seed(draft);
+
+        var data = WizardCallbackData.Choice(WizardStepNames.Capacity, "no_limit");
+        await wizard.HandleInteractionAsync(CallbackInteraction(data, ownerId: draft.OwnerId), draft, CancellationToken.None);
+
+        Assert.Equal(WizardStepNames.Visibility, draft.Step);
+        using var doc = JsonDocument.Parse(draft.PayloadJson);
+        var root = doc.RootElement;
+        Assert.True(root.TryGetProperty("single", out var single));
+        // WizardPayloadJsonContext имеет DefaultIgnoreCondition=WhenWritingNull,
+        // поэтому null-MaxPlayers просто не пишется. Оба варианта
+        // (отсутствует / JsonValueKind.Null) десериализуются обратно в null
+        // и уйдут в БД как NULL — то есть «без лимита».
+        if (single.TryGetProperty("maxPlayers", out var maxPlayers))
+        {
+            Assert.True(
+                maxPlayers.ValueKind == JsonValueKind.Null,
+                $"expected maxPlayers to be null (no limit), got {maxPlayers.ValueKind}");
+        }
+    }
+
     [Fact]
     public async Task ChoiceCallback_FromMismatchedStep_AdvancesBasedOnCallbackStep()
     {

tests/GmRelay.Bot.Tests/Features/Sessions/CreateSession/Wizard/WizardStepRenderTests.cs

@@ -76,6 +76,7 @@ public sealed class WizardStepRenderTests
         var labels = ButtonLabels(kb);
         Assert.Contains(labels, l => l.Contains("Waitlist вкл", StringComparison.Ordinal));
         Assert.Contains(labels, l => l.Contains("Без waitlist", StringComparison.Ordinal));
+        Assert.Contains(labels, l => l.Contains("Без лимита", StringComparison.Ordinal));
     }
 
     [Fact]