review fixes: complete success path, pool capacity navigation, time parser tests

- DiscordWizardSubmitter.SubmitAsync: confirm success, delete draft, clear context.
- GameCreationWizard: pool free-text duration now advances to Capacity.
- PreviousStep(Capacity) returns PoolSystemDuration for pools.
- Remove unused optional IPlatformMessenger/NpgsqlDataSource from submitter.
- Add DiscordTimeParserTests preserving ParseTimeInput coverage.

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

@@ -93,6 +93,48 @@ public sealed class GameCreationWizardStepTransitionsTests
         Assert.Equal(10, maxPlayers.GetInt32());
     }
 
+    [Fact]
+    public async Task PoolSystemDuration_FreeTextDuration_AdvancesToCapacity()
+    {
+        var wizard = BuildWizard(out var drafts, out _);
+        var payload = new WizardPayload
+        {
+            Type = WizardCreationType.Pool,
+            Title = "Pool",
+            System = "Dnd5e",
+        };
+        var draft = NewDraft(WizardStepNames.PoolSystemDuration, payload);
+        drafts.Seed(draft);
+
+        await wizard.HandleInteractionAsync(TextInteraction("4", ownerId: draft.OwnerId), draft, CancellationToken.None);
+
+        Assert.Equal(WizardStepNames.Capacity, draft.Step);
+        using var doc = JsonDocument.Parse(draft.PayloadJson);
+        var root = doc.RootElement;
+        Assert.True(root.TryGetProperty("durationMinutes", out var dur));
+        Assert.Equal(240, dur.GetInt32());
+    }
+
+    [Fact]
+    public async Task Back_FromPoolCapacity_GoesToPoolSystemDuration()
+    {
+        var wizard = BuildWizard(out var drafts, out _);
+        var payload = new WizardPayload
+        {
+            Type = WizardCreationType.Pool,
+            Title = "Pool",
+            System = "Dnd5e",
+            DurationMinutes = 240,
+        };
+        var draft = NewDraft(WizardStepNames.Capacity, payload);
+        drafts.Seed(draft);
+
+        var data = WizardCallbackData.Back();
+        await wizard.HandleInteractionAsync(CallbackInteraction(data, ownerId: draft.OwnerId), draft, CancellationToken.None);
+
+        Assert.Equal(WizardStepNames.PoolSystemDuration, draft.Step);
+    }
+
     [Theory]
     [InlineData("waitlist:on")]
     [InlineData("waitlist:off")]