fix(comm+site): route BrowseOpcUaNodeCommand via DeploymentManagerActor singleton

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

@@ -146,22 +146,13 @@ public class SiteCommunicationActor : ReceiveActor, IWithTimers
         Receive<RouteToSetAttributesRequest>(msg => _deploymentManagerProxy.Forward(msg));
 
         // OPC UA Tag Browser (interactive design-time query) — forward to the
-        // site-local Data Connection Manager actor, which owns the in-memory
-        // map of live data-connection adapters keyed by ConnectionName and
-        // executes the browse against the appropriate OPC UA client. The
-        // manager is not a child of DeploymentManagerActor, so we route via
-        // ActorSelection rather than the _deploymentManagerProxy field; the
-        // path matches the registration in AkkaHostedService. ActorSelection
-        // has no Forward() helper, so we Tell with the original Sender so the
-        // BrowseOpcUaNodeResult routes straight back to the central UI's Ask
-        // (via the CentralCommunicationActor sender chain), not to us.
-        Receive<BrowseOpcUaNodeCommand>(msg =>
-        {
-            _log.Debug(
-                "Routing BrowseOpcUaNodeCommand for connection '{0}' to DataConnectionManager",
-                msg.ConnectionName);
-            Context.ActorSelection("/user/dcl-manager").Tell(msg, Sender);
-        });
+        // Deployment Manager singleton, which always lands on the active site
+        // node. Routing to the site-local /user/dcl-manager directly is wrong
+        // because the standby node has a dcl-manager too, but its
+        // DataConnectionActor children (which own the live OPC UA sessions)
+        // only exist on the singleton's node. The singleton then re-forwards
+        // to its own /user/dcl-manager, which DOES have the connection.
+        Receive<BrowseOpcUaNodeCommand>(msg => _deploymentManagerProxy.Forward(msg));
 
         // Pattern 7: Remote Queries
         Receive<EventLogQueryRequest>(msg =>