feat(home-dialog): per-session suppression tracker

Singleton keyed by ShortUdid; lock on per-viewer set to avoid
cross-viewer contention. Process lifetime — restart re-fires.

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

SVSim.EmulatedEntrypoint/Program.cs

@@ -117,6 +117,10 @@ public class Program
         builder.Services.AddMemoryCache();
         builder.Services.AddSingleton<IDeckCodeService, DeckCodeService>();
 
+        // Per-process per-viewer tracker for home_dialog_list suppression on /mypage/index.
+        // Restart re-fires once per viewer — documented trade in the design spec.
+        builder.Services.AddSingleton<IHomeDialogSessionTracker, HomeDialogSessionTracker>();
+
         #endregion
 
         builder.Services.AddBattleNode(opt =>

SVSim.EmulatedEntrypoint/Services/HomeDialogSessionTracker.cs

@@ -0,0 +1,35 @@
+using System.Collections.Concurrent;
+
+namespace SVSim.EmulatedEntrypoint.Services;
+
+/// <summary>
+/// Records which home_dialog_list entries have already been emitted to which viewer
+/// during the current server-process lifetime. Used by MyPageController to suppress
+/// re-firing the popup on subsequent /mypage/index calls.
+///
+/// Keyed by ShortUdid (stable for the viewer's lifetime), NOT the rotating SID.
+/// Lifetime is the host process — restart re-fires once per viewer (documented trade
+/// in docs/superpowers/specs/2026-06-08-home-dialog-list-design.md §1).
+/// </summary>
+public interface IHomeDialogSessionTracker
+{
+    /// <summary>True iff this dialog has not yet been emitted for this viewer in this
+    /// process. Marks as fired on success.</summary>
+    bool TryReserve(long viewerShortUdid, int dialogId);
+}
+
+public sealed class HomeDialogSessionTracker : IHomeDialogSessionTracker
+{
+    private readonly ConcurrentDictionary<long, HashSet<int>> _firedByViewer = new();
+
+    public bool TryReserve(long viewerShortUdid, int dialogId)
+    {
+        var set = _firedByViewer.GetOrAdd(viewerShortUdid, _ => new HashSet<int>());
+        // HashSet<int> is NOT thread-safe — lock on the per-viewer set instance so
+        // we don't serialize across viewers.
+        lock (set)
+        {
+            return set.Add(dialogId);
+        }
+    }
+}

SVSim.UnitTests/Services/HomeDialogSessionTrackerTests.cs

@@ -0,0 +1,53 @@
+using SVSim.EmulatedEntrypoint.Services;
+
+namespace SVSim.UnitTests.Services;
+
+public class HomeDialogSessionTrackerTests
+{
+    [Test]
+    public void TryReserve_returns_true_first_time_and_false_on_repeat_for_same_viewer_and_dialog()
+    {
+        var tracker = new HomeDialogSessionTracker();
+
+        Assert.That(tracker.TryReserve(viewerShortUdid: 100, dialogId: 1), Is.True);
+        Assert.That(tracker.TryReserve(viewerShortUdid: 100, dialogId: 1), Is.False);
+    }
+
+    [Test]
+    public void TryReserve_is_independent_across_viewers()
+    {
+        var tracker = new HomeDialogSessionTracker();
+
+        Assert.That(tracker.TryReserve(100, 1), Is.True);
+        Assert.That(tracker.TryReserve(200, 1), Is.True, "viewer 200 must see the dialog even though viewer 100 already did");
+    }
+
+    [Test]
+    public void TryReserve_is_independent_across_dialog_ids_for_one_viewer()
+    {
+        var tracker = new HomeDialogSessionTracker();
+
+        Assert.That(tracker.TryReserve(100, 1), Is.True);
+        Assert.That(tracker.TryReserve(100, 2), Is.True);
+        Assert.That(tracker.TryReserve(100, 1), Is.False);
+        Assert.That(tracker.TryReserve(100, 2), Is.False);
+    }
+
+    [Test]
+    public void TryReserve_is_thread_safe_under_concurrent_calls_for_one_viewer()
+    {
+        var tracker = new HomeDialogSessionTracker();
+        const int dialogId = 42;
+        const int parallelism = 200;
+        int trueCount = 0;
+
+        Parallel.For(0, parallelism, _ =>
+        {
+            if (tracker.TryReserve(viewerShortUdid: 1, dialogId: dialogId))
+                Interlocked.Increment(ref trueCount);
+        });
+
+        Assert.That(trueCount, Is.EqualTo(1),
+            "Exactly one thread must win the reservation; the rest must observe false.");
+    }
+}