feat(mesh-phase4): DriverHostActor runs ConfigDb-free (LocalDb alarm store, guarded acks)

Nullable ConfigDb factory; UpsertNodeDeploymentState no-ops when absent
(central persists acks from the ApplyAck); scripted-alarm condition state
served from the LocalDb store instead of the ConfigDb-backed Ef store.
Combines Phase-4 Tasks 4 + 6. Removes the interim dbFactory! cast.

Claude-Session: https://claude.ai/code/session_01GASWkNEi68FSCtvr6rLoEW

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

@@ -18,6 +18,7 @@ using ZB.MOM.WW.OtOpcUa.Commons.OpcUa;
 using ZB.MOM.WW.OtOpcUa.Configuration;
 using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
 using ZB.MOM.WW.OtOpcUa.Core.AlarmHistorian;
+using ZB.MOM.WW.OtOpcUa.Core.ScriptedAlarms;
 using ZB.MOM.WW.OtOpcUa.Core.Scripting;
 using ZB.MOM.WW.OtOpcUa.Core.VirtualTags;
 using ZB.MOM.WW.OtOpcUa.OpcUaServer;
@@ -282,6 +283,12 @@ public static class ServiceCollectionExtensions
             // harnesses) rather than given a null-object, so DriverHostActor skips caching outright
             // instead of pretending to cache into a sink that drops everything.
             var deploymentArtifactCache = resolver.GetService<IDeploymentArtifactCache>();
+            // Per-cluster mesh Phase 4: scripted-alarm condition-state store. Registered by the Host's
+            // AddOtOpcUaLocalDb on driver-role nodes (the replicated LocalDb store), so condition state
+            // persists with no ConfigDb; null elsewhere (admin-only graphs, test harnesses) → the actor
+            // falls back to an EfAlarmConditionStateStore over dbFactory, or skips the alarm host when
+            // there is no ConfigDb either.
+            var alarmStateStore = resolver.GetService<IAlarmStateStore>();
             // Per-cluster mesh Phase 3: ConfigSource:Mode selects where this driver reads config.
             // FetchAndCache pulls the artifact from central over gRPC and reads only the LocalDb cache;
             // Direct (default) reads central SQL as before. The fetcher is resolved only in FetchAndCache
@@ -462,14 +469,12 @@ public static class ServiceCollectionExtensions
                 // ackRouter: under ClusterClient mode the node comm actor relays ApplyAcks across
                 // the boundary; under Dps it stays null and the host publishes on the
                 // deployment-acks topic exactly as before.
-                // dbFactory! — KNOWN INTERIM. A driver-only node genuinely passes a null factory here
-                // (ConfigDb is now gated on hasAdmin, and driver-only nodes are forced to FetchAndCache),
-                // so DriverHostActor's ConfigDb-touching paths — scripted-alarm state persistence
-                // (EfAlarmConditionStateStore) and UpsertNodeDeploymentState — fault-and-swallow until
-                // Task 4 makes the factory nullable + guards those sites (and removes this !) and Task 6
-                // re-homes the alarm store to LocalDb. Inert in practice: no driver-only node is
-                // configured to boot until the Task 10 rig change.
-                DriverHostActor.Props(dbFactory!, roleInfo.LocalNode,
+                // dbFactory is nullable (Phase 4): a driver-only node passes null here — ConfigDb is
+                // gated on hasAdmin and driver-only nodes are forced to FetchAndCache. DriverHostActor
+                // guards every ConfigDb-touching path on it (UpsertNodeDeploymentState no-ops; central
+                // persists acks from the ApplyAck) and serves scripted-alarm state from the LocalDb
+                // alarmStateStore instead of an EfAlarmConditionStateStore.
+                DriverHostActor.Props(dbFactory, roleInfo.LocalNode,
                     ackRouter: useClusterClient ? nodeComm : null,
                     driverFactory: driverFactory, localRoles: roleInfo.LocalRoles,
                     dependencyMux: mux,
@@ -484,7 +489,8 @@ public static class ServiceCollectionExtensions
                     redundancyRoleView: redundancyRoleView,
                     replicationPeerHost: replicationPeerHost,
                     fetchAndCacheMode: fetchAndCacheMode,
-                    artifactFetcher: artifactFetcher),
+                    artifactFetcher: artifactFetcher,
+                    alarmStateStore: alarmStateStore),
                 DriverHostActorName);
             registry.Register<DriverHostActorKey>(driverHost);