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

src/ScadaLink.Communication/Actors/DebugStreamBridgeActor.cs

@@ -183,6 +183,15 @@ public class DebugStreamBridgeActor : ReceiveActor, IWithTimers
             return;
         }
 
+        // Unsubscribe the failed stream on the *previous* endpoint before reconnecting.
+        // This cancels the local subscription CTS and -- where the channel is still
+        // alive -- propagates gRPC cancellation to the site so its SiteStreamGrpcServer
+        // stops the StreamRelayActor for this correlation ID, rather than leaving a
+        // zombie relay actor until TCP RST / keepalive eventually detects the loss.
+        var previousEndpoint = _useNodeA ? _grpcNodeAAddress : _grpcNodeBAddress;
+        var previousClient = _grpcFactory.GetOrCreate(_siteIdentifier, previousEndpoint);
+        previousClient.Unsubscribe(_correlationId);
+
         // Flip to the other node
         _useNodeA = !_useNodeA;