fix(comm): heartbeat IsActive uses the shared oldest-Up predicate; Host wires one delegate everywhere (plan R2-02 T4)

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

@@ -67,10 +67,10 @@ public class SiteCommunicationActor : ReceiveActor, IWithTimers
     /// <param name="deploymentManagerProxy">Local reference to the Deployment Manager singleton proxy.</param>
     /// <param name="isActiveCheck">
     /// Optional override returning <c>true</c> when this node
-    /// is the active member of the site cluster. <c>null</c> uses the real
-    /// Akka <see cref="Cluster"/> leader check (the default for production
-    /// wiring); tests pass a stub so they do not need to load Akka.Cluster
-    /// into the <c>TestKit</c> ActorSystem.
+    /// is the active member of the site cluster. <c>null</c> uses the shared oldest-Up
+    /// evaluator (production wiring passes the Host's singleton-host delegate); tests
+    /// pass a stub so they do not need to load Akka.Cluster into the <c>TestKit</c>
+    /// ActorSystem.
     /// </param>
     public SiteCommunicationActor(
         string siteId,
@@ -506,24 +506,16 @@ public class SiteCommunicationActor : ReceiveActor, IWithTimers
     }
 
     /// <summary>
-    /// Default active-node check used when no override is
-    /// supplied. Mirrors <c>ActiveNodeGate</c> in the Host (and
-    /// <c>ActiveNodeHealthCheck</c>): the node is the active member of the
-    /// site cluster when it is the current cluster leader AND its own
-    /// <see cref="MemberStatus"/> is <see cref="MemberStatus.Up"/>. Any other
-    /// state (still joining, leaving, no leader yet) reports standby —
-    /// safe-by-default, matching the standby case.
+    /// Default active-node check used when no override is supplied: oldest-Up member
+    /// semantics via the shared <see cref="ClusterState.ActiveNodeEvaluator"/> — the
+    /// same predicate as the S&F delivery gate and the replication resync authority
+    /// (review 02 round 2, N1). Unscoped by role: a site cluster's members all carry
+    /// the site role, so role scoping is a no-op here; production wiring passes the
+    /// Host's role-scoped IClusterNodeProvider delegate anyway. Any other state
+    /// (still joining, leaving) reports standby — safe-by-default.
     /// </summary>
-    private bool DefaultIsActiveCheck()
-    {
-        var cluster = Cluster.Get(Context.System);
-        var self = cluster.SelfMember;
-        if (self.Status != MemberStatus.Up)
-            return false;
-
-        var leader = cluster.State.Leader;
-        return leader != null && leader == self.Address;
-    }
+    private bool DefaultIsActiveCheck() =>
+        ClusterState.ActiveNodeEvaluator.SelfIsOldestUp(Cluster.Get(Context.System));
 
     // ── Internal messages ──
 

src/ZB.MOM.WW.ScadaBridge.Host/Actors/AkkaHostedService.cs

@@ -833,7 +833,8 @@ akka {{
             Props.Create(() => new SiteCommunicationActor(
                 _nodeOptions.SiteId!,
                 _communicationOptions,
-                dmProxy)),
+                dmProxy,
+                activeNodeCheck)),
             "site-communication");
 
         // Register local handlers with SiteCommunicationActor