refactor(fleet): #542 delete the dead fleet-status chain (broadcaster, SignalR bridge, hub, messages)

#542 filed FleetStatusBroadcaster as blind to site nodes since the Phase 6 per-cluster mesh
split: it derives "the fleet" from central's own Akka gossip ring, which after the split is
just central's own pair. Scoping the cross-mesh rewrite found the deeper truth — the whole
chain is dead end to end, so this deletes it rather than reviving it.

  - Zero consumers. FleetStatusBroadcaster published FleetStatusChanged on the DPS
    "fleet-status" topic; FleetStatusSignalRBridge forwarded it to FleetStatusHub
    ("/hubs/fleet-status"); nothing anywhere connected. The AdminUI bans self-connecting
    HubConnections, no browser JS subscribes, and /fleet (Fleet.razor) reads
    NodeDeploymentState from the ConfigDb plus IClusterRoleInfo on a 5 s poll instead.
  - Its second input never existed. DriverHostStatusHeartbeat had no production sender —
    only the broadcaster's own test told it — so CurrentRevision was always null and the
    30 s staleness -> Degraded flip could never fire.
  - Post-Phase-6 DPS is pair-local, so even the central-only view it did produce was an
    accident of topology rather than a design.

The fleet visibility that actually works is unchanged and already cross-mesh-correct:
/fleet over NodeDeploymentState, and the four Phase 5 per-node telemetry dials.

Precedent for deleting inert machinery rather than activating it: #522 (driver stability
tiers), #507 (discovered-node injection), #525 (GetMemoryFootprint).

Deleted: FleetStatusBroadcaster (+ its nested DriverHostStatusHeartbeat), its admin
singleton registration and FleetStatusBroadcasterKey, FleetStatusSignalRBridge and its
key, FleetStatusHub and its route mapping, and the FleetStatusChanged / FleetNodeStatus /
FleetNodeHealth messages. Both Fleet/ directories survive — ControlPlane keeps
ClusterNodeAddressReconciler, Commons keeps GetDiagnostics. Docs swept where they claimed
a fleet-status channel exists (Telemetry.md's Phase 5 non-migrated channels,
Configuration.md, CLAUDE.md); completed-program plan docs under docs/plans and docs/v2 are
left as the historical record they are.

Build 0 errors, 868 warnings — byte-identical to master's rebuild baseline.
ControlPlane.Tests 231/231, AdminUI.Tests 1109/1109.

Claude-Session: https://claude.ai/code/session_014WNM4vjoVksyyBraTXSZE1

src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/ServiceCollectionExtensions.cs

@@ -26,12 +26,11 @@ public static class ServiceCollectionExtensions
     public const string ConfigPublishSingletonName = "config-publish";
     public const string AdminOperationsSingletonName = "admin-operations";
     public const string AuditWriterSingletonName = "audit-writer";
-    public const string FleetStatusSingletonName = "fleet-status";
     public const string RedundancyStateSingletonName = "redundancy-state";
     public const string ClusterNodeAddressReconcilerSingletonName = "cluster-node-address-reconciler";
 
     /// <summary>
-    /// Registers the admin-role cluster singletons on the AkkaConfigurationBuilder — five with
+    /// Registers the admin-role cluster singletons on the AkkaConfigurationBuilder — three with
     /// registry proxies, plus the address reconciler, which is proxy-less because nothing addresses it.
     /// Must be called against the same builder used by <c>AkkaHostedService</c> so the singletons
     /// share the host's ActorSystem.
@@ -139,10 +138,11 @@ public static class ServiceCollectionExtensions
             },
             singletonOptions);
 
-        builder.WithSingleton<FleetStatusBroadcasterKey>(
-            FleetStatusSingletonName,
-            (system, registry, resolver) => FleetStatusBroadcaster.Props(),
-            singletonOptions);
+        // Gitea #542 (2026-08-06): the fleet-status singleton is NO LONGER registered here — the
+        // whole FleetStatusBroadcaster → DPS → SignalR bridge → FleetStatusHub chain was DELETED.
+        // It had zero clients end-to-end (no browser JS, no HubConnection — /fleet reads
+        // NodeDeploymentState from the ConfigDb on a poll), its DriverHostStatusHeartbeat input had
+        // no production sender, and after mesh Phase 6 its "fleet" was only central's own pair.
 
         // Per-cluster mesh Phase 6: the redundancy-state singleton is NO LONGER registered here.
         // It was an admin-scoped, fleet-wide singleton — one Primary elected across the whole mesh.
@@ -253,7 +253,6 @@ public static class ServiceCollectionExtensions
 public sealed class ConfigPublishCoordinatorKey { }
 public sealed class AdminOperationsActorKey { }
 public sealed class AuditWriterActorKey { }
-public sealed class FleetStatusBroadcasterKey { }
 public sealed class RedundancyStateActorKey { }
 public sealed class ClusterNodeAddressReconcilerKey { }
 public sealed class CentralCommunicationActorKey { }