test(communication): M2.11 review nits — bridge-actor not-found test + dead-letter comment + toast wording (#24)

- Add DebugStreamBridgeActorTests: On_InstanceNotFound_Snapshot_Forwards_To_OnEvent_Does_Not_Open_Stream_And_Terminates — asserts _onEvent receives the not-found snapshot, SubscribeCalls remains empty, and the actor terminates cleanly via Watch/ExpectTerminated.
- Add comment in DebugStreamBridgeActor near Context.Stop(Self) explaining that the subsequent StopDebugStream Tell from DebugStreamService.StopStream produces a benign expected dead-letter.
- Reword not-found toast in DebugView.razor to "Instance not found on the selected site — check the deployment target." (accurate when the instance may be deployed to a different site).

src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Pages/Deployment/DebugView.razor

@@ -451,8 +451,7 @@
             {
                 DebugStreamService.StopStream(session.SessionId);
                 _toast.ShowError(
-                    $"Instance is not deployed on that site. " +
-                    $"Deploy it first or choose the correct site.");
+                    "Instance not found on the selected site — check the deployment target.");
                 _connecting = false;
                 return;
             }

src/ZB.MOM.WW.ScadaBridge.Communication/Actors/DebugStreamBridgeActor.cs

@@ -98,6 +98,10 @@ public class DebugStreamBridgeActor : ReceiveActor, IWithTimers
                     _instanceUniqueName);
                 _stopped = true;
                 _onEvent(snapshot); // resolves the snapshot TCS with InstanceNotFound=true
+                // Note: after Context.Stop(Self) below the actor is dead. DebugStreamService
+                // inspects InitialSnapshot.InstanceNotFound and calls StopStream, which sends
+                // a StopDebugStream message. That Tell arrives after the actor has already
+                // stopped, producing a benign Akka dead-letter — expected and harmless.
                 Context.Stop(Self);
                 return;
             }

tests/ZB.MOM.WW.ScadaBridge.Communication.Tests/Grpc/DebugStreamBridgeActorTests.cs

@@ -60,6 +60,44 @@ public class DebugStreamBridgeActorTests : TestKit
         return new TestContext(actor, commProbe, mockClient, events, terminated);
     }
 
+    [Fact]
+    public void On_InstanceNotFound_Snapshot_Forwards_To_OnEvent_Does_Not_Open_Stream_And_Terminates()
+    {
+        // M2.11: when the site reports InstanceNotFound=true the bridge actor must
+        // (a) forward the not-found snapshot to _onEvent so DebugStreamService's TCS
+        //     resolves and the caller can inspect the flag,
+        // (b) NOT open a gRPC stream (SubscribeCalls must remain empty), and
+        // (c) stop itself cleanly.
+        var ctx = CreateBridgeActor();
+        ctx.CommProbe.ExpectMsg<SiteEnvelope>(); // initial subscribe envelope
+
+        var notFoundSnapshot = new DebugViewSnapshot(
+            InstanceName,
+            new List<AttributeValueChanged>(),
+            new List<AlarmStateChanged>(),
+            DateTimeOffset.UtcNow,
+            InstanceNotFound: true);
+
+        Watch(ctx.BridgeActor);
+        ctx.BridgeActor.Tell(notFoundSnapshot);
+
+        // (a) _onEvent must receive the not-found snapshot
+        AwaitCondition(() => { lock (ctx.ReceivedEvents) { return ctx.ReceivedEvents.Count == 1; } },
+            TimeSpan.FromSeconds(3));
+        lock (ctx.ReceivedEvents)
+        {
+            var received = Assert.IsType<DebugViewSnapshot>(ctx.ReceivedEvents[0]);
+            Assert.True(received.InstanceNotFound);
+        }
+
+        // (b) no gRPC stream opened
+        ExpectTerminated(ctx.BridgeActor, TimeSpan.FromSeconds(3));
+        Assert.Empty(ctx.MockGrpcClient.SubscribeCalls);
+
+        // (c) actor terminates cleanly
+        // ExpectTerminated above already verified termination
+    }
+
     [Fact]
     public void PreStart_Sends_SubscribeDebugViewRequest_Via_ClusterClient()
     {