refactor(host): CentralSingletonRegistrar -> SingletonRegistrar with optional role scope — unblocks site-singleton drains (plan R2-01 T10)

tests/ZB.MOM.WW.ScadaBridge.Host.Tests/CoordinatedShutdownTests.cs

@@ -51,9 +51,9 @@ public class CoordinatedShutdownTests
 
         // Review 01 [Medium]: notification-outbox and audit-log-ingest were the
         // only central singletons WITHOUT a cluster-leave drain task. All seven
-        // now go through CentralSingletonRegistrar.Start, which always adds the
+        // now go through SingletonRegistrar.Start, which always adds the
         // PhaseClusterLeave GracefulStop drain.
-        Assert.Contains("CentralSingletonRegistrar.Start(", content);
+        Assert.Contains("SingletonRegistrar.Start(", content);
         foreach (var name in new[] { "notification-outbox", "audit-log-ingest", "site-call-audit",
                                      "audit-log-purge", "site-audit-reconciliation",
                                      "kpi-history-recorder", "pending-deployment-purge" })

tests/ZB.MOM.WW.ScadaBridge.Host.Tests/SingletonRegistrarTests.cs

@@ -5,7 +5,7 @@ using ZB.MOM.WW.ScadaBridge.Host.Actors;
 
 namespace ZB.MOM.WW.ScadaBridge.Host.Tests;
 
-public class CentralSingletonRegistrarTests
+public class SingletonRegistrarTests
 {
     private sealed class EchoActor : ReceiveActor
     {
@@ -16,7 +16,7 @@ public class CentralSingletonRegistrarTests
     public async Task Start_CreatesManagerAndProxy_WithCanonicalNames_AndDrainTask()
     {
         using var system = CreateSingleNodeClusterSystem();
-        var handle = CentralSingletonRegistrar.Start(
+        var handle = SingletonRegistrar.Start(
             system, "test-widget", Props.Create(() => new EchoActor()),
             NullLogger.Instance, drainTimeout: TimeSpan.FromSeconds(2));
 
@@ -36,6 +36,25 @@ public class CentralSingletonRegistrarTests
         Assert.True(handle.Manager.IsNobody() || system.WhenTerminated.IsCompleted);
     }
 
+    [Fact]
+    public async Task Start_WithRoleScope_CreatesRoleScopedSingleton_ThatAnswers()
+    {
+        // Round-2 N5: role scoping is what kept the two SITE singletons
+        // (deployment-manager, event-log-handler) hand-rolled and drain-less.
+        using var system = CreateSingleNodeClusterSystem(); // roles = ["Central"]
+        var handle = SingletonRegistrar.Start(
+            system, "role-widget", Props.Create(() => new EchoActor()),
+            NullLogger.Instance, drainTimeout: TimeSpan.FromSeconds(2), role: "Central");
+
+        Assert.EndsWith("/user/role-widget-singleton", handle.Manager.Path.ToString());
+        Assert.EndsWith("/user/role-widget-proxy", handle.Proxy.Path.ToString());
+
+        // The node holds the role => manager instantiates the singleton and
+        // the role-scoped proxy resolves it.
+        var echo = await handle.Proxy.Ask<string>("hi", TimeSpan.FromSeconds(20));
+        Assert.Equal("hi", echo);
+    }
+
     private static ActorSystem CreateSingleNodeClusterSystem()
     {
         var port = FreePort();