fix(ui): disposal guard on Alarm Summary live callback, matching the DebugView pattern (plan R2-07 T9)

tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/Monitoring/AlarmSummaryRenderTests.cs

@@ -278,6 +278,30 @@ public class AlarmSummaryRenderTests : BunitContext
         });
     }
 
+    // ── arch-review R2 N7: disposal guard on the live callback ─────────────────
+
+    [Fact]
+    public void LiveCallbackRacingDispose_IsDropped_NoRebuildNoThrow()
+    {
+        var cut = RenderWithSiteSelected();
+        _liveCache.PushAlarms(new List<AlarmStateChanged>
+        {
+            new("Gamma", "G-alarm", AlarmState.Active, 300, DateTimeOffset.UtcNow),
+        });
+        cut.WaitForAssertion(() => Assert.Equal("Gamma", FirstRowInstance(cut)));
+
+        // Snapshot the callback BEFORE disposal — this models a delta thread that
+        // already read the delegate when Dispose ran (arch-review R2 N7).
+        var inFlight = _liveCache.CapturedCallback!;
+        cut.Instance.Dispose();
+
+        _liveCache.PushAlarms(new List<AlarmStateChanged>()); // mutate the fake's snapshot
+        var ex = Record.Exception(inFlight);
+        Assert.Null(ex);
+        // The disposed page must not have re-applied the (now empty) live snapshot.
+        Assert.Equal("Gamma", FirstRowInstance(cut));
+    }
+
     /// <summary>
     /// Controllable in-memory fake of <see cref="ISiteAlarmLiveCache"/>: records
     /// subscribe/dispose counts and lets a test push a live snapshot (which flips
@@ -293,6 +317,7 @@ public class AlarmSummaryRenderTests : BunitContext
         public int SubscribeCount { get; private set; }
         public int DisposeCount { get; private set; }
         public int? LastSubscribedSite { get; private set; }
+        public Action? CapturedCallback => _onChanged;
 
         public IDisposable Subscribe(int siteId, Action onChanged)
         {