fix(communication): resolve Communication-002/003 — gRPC reconnect stream cleanup and subscription map safety

tests/ScadaLink.Communication.Tests/Grpc/DebugStreamBridgeActorTests.cs

@@ -159,6 +159,34 @@ public class DebugStreamBridgeActorTests : TestKit
         Assert.Equal("corr-1", ctx.MockGrpcClient.SubscribeCalls[1].CorrelationId);
     }
 
+    [Fact]
+    public void On_GrpcError_Unsubscribes_Old_Stream_Before_Reconnect()
+    {
+        // Communication-002 regression: a reconnect must unsubscribe the previous
+        // stream so the old node does not keep a zombie relay actor / subscription.
+        var ctx = CreateBridgeActor();
+        ctx.CommProbe.ExpectMsg<SiteEnvelope>();
+
+        var snapshot = new DebugViewSnapshot(
+            InstanceName,
+            new List<AttributeValueChanged>(),
+            new List<AlarmStateChanged>(),
+            DateTimeOffset.UtcNow);
+
+        ctx.BridgeActor.Tell(snapshot);
+        AwaitCondition(() => ctx.MockGrpcClient.SubscribeCalls.Count == 1, TimeSpan.FromSeconds(3));
+
+        // Simulate gRPC error → reconnect
+        ctx.MockGrpcClient.SubscribeCalls[0].OnError(new Exception("Stream broken"));
+
+        // Should resubscribe...
+        AwaitCondition(() => ctx.MockGrpcClient.SubscribeCalls.Count == 2, TimeSpan.FromSeconds(5));
+
+        // ...and must have unsubscribed the prior correlation ID so the old node's
+        // relay actor is released rather than left zombie.
+        Assert.Contains("corr-1", ctx.MockGrpcClient.UnsubscribedCorrelationIds);
+    }
+
     [Fact]
     public void After_MaxRetries_Terminates()
     {