fix(communication): resolve Communication-004..008 — Resume supervision, gRPC option wiring, address-load logging, sync dispose, flap detection

src/ScadaLink.Communication/Actors/CentralCommunicationActor.cs

@@ -84,6 +84,15 @@ public class CentralCommunicationActor : ReceiveActor
         // Periodic refresh trigger
         Receive<RefreshSiteAddresses>(_ => LoadSiteAddressesFromDb());
 
+        // Communication-006: a faulted LoadSiteAddressesFromDb task is piped here as a
+        // Status.Failure. Without this handler the failure was an unhandled message
+        // (debug-level only) and the refresh failed silently — operators could not
+        // distinguish "no sites configured" from "database is down". Log at Warning.
+        Receive<Status.Failure>(failure =>
+            _log.Warning(failure.Cause,
+                "Failed to load site addresses from the database; the site ClusterClient "
+                + "cache was not refreshed and may be stale or empty"));
+
         // Health monitoring: heartbeats and health reports from sites
         Receive<HeartbeatMessage>(HandleHeartbeat);
         Receive<SiteHealthReport>(HandleSiteHealthReport);
@@ -296,6 +305,25 @@ public class CentralCommunicationActor : ReceiveActor
         }
     }
 
+    /// <summary>
+    /// Coordinator supervision strategy (CLAUDE.md: "Resume for coordinator actors").
+    /// CentralCommunicationActor is a long-lived coordinator that owns the per-site
+    /// ClusterClient map; a transient fault in a child (e.g. a ClusterClient child)
+    /// must Resume so the child's connection state is preserved rather than wiped by
+    /// a Restart.
+    /// </summary>
+    protected override SupervisorStrategy SupervisorStrategy()
+    {
+        return new OneForOneStrategy(
+            maxNrOfRetries: -1,
+            withinTimeRange: Timeout.InfiniteTimeSpan,
+            decider: Decider.From(ex =>
+            {
+                _log.Warning(ex, "Child actor of CentralCommunicationActor faulted, resuming (state preserved)");
+                return Directive.Resume;
+            }));
+    }
+
     protected override void PreStart()
     {
         _log.Info("CentralCommunicationActor started");