feat: implement DiscordSessionBatchRenderer for Embed and Buttons

- Render SessionBatchViewModel into NetCord EmbedProperties + ActionRowProperties
- One embed per session with game title, Moscow date, players, capacity, waitlist, status
- Buttons map AvailableAction to ButtonProperties with platform-neutral custom IDs
- Cancelled sessions get embed but no action row
- Full sessions trigger waitlist button label
- 7 tests covering open/full/waitlist/cancelled/reschedule states

Closes #27

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/GmRelay.DiscordBot/Rendering/DiscordSessionBatchRenderer.cs

@@ -0,0 +1,125 @@
+using GmRelay.Shared.Domain;
+using GmRelay.Shared.Rendering;
+using NetCord;
+using NetCord.Rest;
+
+namespace GmRelay.DiscordBot.Rendering;
+
+public static class DiscordSessionBatchRenderer
+{
+    public static (IReadOnlyList<EmbedProperties> Embeds, IReadOnlyList<ActionRowProperties> ActionRows) Render(SessionBatchViewModel view)
+    {
+        var embeds = new List<EmbedProperties>();
+        var actionRows = new List<ActionRowProperties>();
+
+        foreach (var session in view.Sessions)
+        {
+            var embed = BuildEmbed(view.Title, session);
+            embeds.Add(embed);
+
+            if (session.AvailableActions.Count > 0)
+            {
+                var actionRow = new ActionRowProperties();
+                foreach (var action in session.AvailableActions)
+                {
+                    actionRow.Add(new ButtonProperties(
+                        $"{action.ActionKey}:{action.SessionId}",
+                        action.Label,
+                        ButtonStyle.Primary));
+                }
+                actionRows.Add(actionRow);
+            }
+        }
+
+        return (embeds, actionRows);
+    }
+
+    private static EmbedProperties BuildEmbed(string title, SessionViewItem session)
+    {
+        var embed = new EmbedProperties()
+            .WithTitle($"{title} — {session.ScheduledAt.FormatMoscow()}");
+
+        if (SessionStatus.IsCancelled(session.Status))
+        {
+            embed = embed.WithDescription("❌ Сессия отменена");
+        }
+        else
+        {
+            embed = embed.WithDescription(BuildPlayerDescription(session));
+        }
+
+        var fields = new List<EmbedFieldProperties>
+        {
+            new EmbedFieldProperties()
+                .WithName("👥 Заполненность")
+                .WithValue(session.MaxPlayers.HasValue
+                    ? $"{session.ActivePlayerCount}/{session.MaxPlayers.Value}"
+                    : $"{session.ActivePlayerCount}")
+                .WithInline(),
+
+            new EmbedFieldProperties()
+                .WithName("⏳ Лист ожидания")
+                .WithValue(session.WaitlistedPlayers.Count > 0
+                    ? session.WaitlistedPlayers.Count.ToString()
+                    : "—")
+                .WithInline(),
+
+            new EmbedFieldProperties()
+                .WithName("📊 Статус")
+                .WithValue(FormatStatus(session.Status))
+                .WithInline()
+        };
+
+        if (!string.IsNullOrEmpty(session.JoinLink))
+        {
+            embed = embed.WithUrl(session.JoinLink);
+        }
+
+        embed = embed.WithColor(GetColor(session));
+        embed = embed.AddFields(fields);
+
+        return embed;
+    }
+
+    private static string BuildPlayerDescription(SessionViewItem session)
+    {
+        if (session.ActivePlayers.Count == 0)
+            return "👥 Пока никто не записался";
+
+        var lines = session.ActivePlayers
+            .Select(p => $"• {p.DisplayName}")
+            .ToList();
+
+        if (session.WaitlistedPlayers.Count > 0)
+        {
+            lines.Add("");
+            lines.Add($"⏳ Лист ожидания ({session.WaitlistedPlayers.Count}):");
+            lines.AddRange(session.WaitlistedPlayers.Select(p => $"• {p.DisplayName}"));
+        }
+
+        return string.Join('\n', lines);
+    }
+
+    private static string FormatStatus(string status) => status switch
+    {
+        SessionStatus.Planned => "Запланирована",
+        SessionStatus.ConfirmationSent => "Ожидает подтверждения",
+        SessionStatus.Confirmed => "Подтверждена",
+        SessionStatus.Cancelled => "Отменена",
+        _ => status
+    };
+
+    private static Color GetColor(SessionViewItem session)
+    {
+        if (SessionStatus.IsCancelled(session.Status))
+            return new Color(0xED4245);
+
+        if (session.Status == SessionStatus.Confirmed)
+            return new Color(0x5865F2);
+
+        if (session.MaxPlayers.HasValue && session.ActivePlayerCount >= session.MaxPlayers.Value)
+            return new Color(0xFEE75C);
+
+        return new Color(0x57F287);
+    }
+}

src/GmRelay.Shared/Rendering/DiscordSessionBatchRenderer.cs

@@ -1,13 +0,0 @@
-namespace GmRelay.Shared.Rendering;
-
-/// <summary>
-/// Заглушка для Discord-рендерера.
-/// Реальная реализация будет добавлена в проект GmRelay.DiscordBot (issue #26).
-/// </summary>
-public static class DiscordSessionBatchRenderer
-{
-    public static object Render(SessionBatchViewModel view)
-    {
-        throw new NotImplementedException("Discord renderer will be implemented in issue #26.");
-    }
-}

tests/GmRelay.Bot.Tests/Rendering/DiscordSessionBatchRendererTests.cs

@@ -35,17 +35,17 @@ public sealed class DiscordSessionBatchRendererTests
         Assert.Equal(2, actionRows.Count); // cancelled skipped
 
         // Embed titles contain game title and Moscow date
-        Assert.Contains(embeds, e => e.Title.Contains("Campaign") && e.Title.Contains("26"));
-        Assert.Contains(embeds, e => e.Title.Contains("Campaign") && e.Title.Contains("27"));
-        Assert.Contains(embeds, e => e.Title.Contains("Campaign") && e.Title.Contains("28"));
+        Assert.Contains(embeds, e => e.Title!.Contains("Campaign") && e.Title.Contains("26"));
+        Assert.Contains(embeds, e => e.Title!.Contains("Campaign") && e.Title.Contains("27"));
+        Assert.Contains(embeds, e => e.Title!.Contains("Campaign") && e.Title.Contains("28"));
 
         // Cancelled session embed description indicates cancellation
-        var cancelledEmbed = embeds.First(e => e.Description.Contains("отменена") || e.Description.Contains("Отменена"));
+        var cancelledEmbed = embeds.First(e => e.Description!.Contains("отменена") || e.Description.Contains("Отменена"));
         Assert.NotNull(cancelledEmbed);
 
         // Active session embeds contain player names
-        Assert.Contains(embeds, e => e.Description != null && e.Description.Contains("Alice"));
-        Assert.Contains(embeds, e => e.Description != null && e.Description.Contains("Charlie"));
+        Assert.Contains(embeds, e => e.Description!.Contains("Alice"));
+        Assert.Contains(embeds, e => e.Description!.Contains("Charlie"));
 
         // Buttons for active sessions
         var allButtons = actionRows.SelectMany(r => r).OfType<ButtonProperties>().ToList();
@@ -94,7 +94,7 @@ public sealed class DiscordSessionBatchRendererTests
         var view = SessionBatchViewBuilder.Build("Test", sessions, participants);
         var (embeds, _) = DiscordSessionBatchRenderer.Render(view);
 
-        Assert.Equal(0xED4245, embeds[0].Color!.Value.RawValue);
+        Assert.Equal(0xED4245, embeds[0].Color.RawValue);
     }
 
     [Fact]
@@ -107,7 +107,7 @@ public sealed class DiscordSessionBatchRendererTests
         var view = SessionBatchViewBuilder.Build("Test", sessions, participants);
         var (embeds, _) = DiscordSessionBatchRenderer.Render(view);
 
-        Assert.Equal(0x57F287, embeds[0].Color!.Value.RawValue);
+        Assert.Equal(0x57F287, embeds[0].Color.RawValue);
     }
 
     [Fact]
@@ -120,7 +120,7 @@ public sealed class DiscordSessionBatchRendererTests
         var view = SessionBatchViewBuilder.Build("Test", sessions, participants);
         var (embeds, _) = DiscordSessionBatchRenderer.Render(view);
 
-        Assert.Equal(0xFEE75C, embeds[0].Color!.Value.RawValue);
+        Assert.Equal(0xFEE75C, embeds[0].Color.RawValue);
     }
 
     [Fact]