feat(runtime): #113 DependencyMuxActor — drivers → virtual-tag fan-out

End-to-end data path is now wired on the read side: driver subscriptions
fire AttributeValuePublished → DriverHostActor → DependencyMuxActor →
DependencyValueChanged to every interested VirtualTagActor. Previously
the publish hit a dead-letter at the host.

DependencyMuxActor:
  - Per-node fan-out router. Maintains tagRef → Set<IActorRef> with a
    reverse subscriber → refs index so unregister/replace are O(refs).
  - Watches subscribers; Terminated triggers automatic unregister so
    dead virtual-tag actors stop receiving publishes.
  - Re-register replaces the prior interest set — no stale-ref leaks
    on actor restart.
  - Drops publishes for refs with no interested subscribers.

VirtualTagActor:
  - New Props params: dependencyRefs + mux ActorRef.
  - PreStart sends RegisterInterest to the mux; PostStop sends
    UnregisterInterest. Default both null so older callers stay quiet.

DriverHostActor:
  - New dependencyMux Props param. Steady + Applying states now
    receive AttributeValuePublished from their DriverInstance children
    and forward to the mux. Null mux is a no-op (dev/Mac).

ServiceCollectionExtensions:
  - WithOtOpcUaRuntimeActors spawns DependencyMuxActor before
    DriverHostActor and threads its ActorRef into the host's Props.
    New DependencyMuxActorKey + DependencyMuxActorName.

Tests: Runtime 57 -> 63 (+6):
- Mux forwards to only subscribers interested in each ref
- Publish for unregistered ref is dropped silently
- Unregister stops forwarding
- Re-register replaces prior interest set
- VirtualTagActor PreStart registration drives end-to-end eval
  (uses AwaitAssert to race-safely settle the PreStart Tell)
- DriverHostActor forwards AttributeValuePublished through to mux

All 6 v2 test suites green: 163 tests passing.

F8 (#79) state updated — dep subscribe seam shipped, Core.VirtualTags
production engine binding (compile + ITagUpstreamSource subscribe) is
the residual.

docs/plans/2026-05-26-akka-hosting-alignment-plan.md.tasks.json

@@ -82,7 +82,7 @@
     {"id": "F5", "subject": "Follow-up: ConfigPublishCoordinator multi-node happy-path test", "status": "completed", "classification": "standard", "estMinutes": 30, "parallelizableWith": [], "blockedBy": [], "commit": "5cfbe8b", "deviation": "Delivered by Task 59 — DeployHappyPathTests.StartDeployment_seals_after_both_nodes_apply exercises the exact 'dispatch to N driver nodes, all ack, seals' flow via the real 2-node TwoNodeClusterHarness rather than a multi-system TestKit. Cleaner because it tests the production code path end-to-end.", "origin": "Self-review of Task 30 — single-ActorSystem TestKit can't simulate the plan's 'dispatch to N driver nodes, all ack, seals' happy path because DiscoverDriverNodes() needs real cluster membership. Add a multi-system test (two ActorSystems joined into one cluster, driver-role on the second)."},
     {"id": "F6", "subject": "Follow-up: RedundancyStateActor publisher abstraction so tests don't need DPS bootstrap", "status": "completed", "classification": "small", "estMinutes": 10, "parallelizableWith": [], "blockedBy": [], "commit": "dfc143c", "origin": "Self-review of Task 35 — RedundancyStateActorTests are skipped because single-node DistributedPubSub bootstrap is unreliable in TestKit. Inject an Action<object> broadcast so tests can replace it with a probe; un-skip both tests."},
     {"id": "F7", "subject": "Follow-up: DriverInstanceActor full engine wiring (subscriptions, writes, ApplyDelta diff)", "status": "completed", "classification": "standard", "estMinutes": 45, "parallelizableWith": [], "blockedBy": [44], "origin": "Self-review of Task 41 — subscription publishing, ApplyDelta diffing, bad-quality-on-disconnect, write path, and supervisor backoff are stubbed. Wire after OpcUaPublishActor lands.", "shipped": "All three pieces landed: (1) spawn lifecycle in DriverHostActor (DriverSpawnPlanner + IDriverFactory seam) — da14149, (2) ISubscribable wiring + OPC UA status-code → OpcUaQuality severity-bit mapping + DetachSubscription on disconnect/PostStop, (3) IWritable.WriteAsync write path with 5s timeout, status-code bubble-up, and AttributeValuePublished published to parent on every OnDataChange — both shipped in the F7-residual batch. Host DI binding (DriverFactoryBootstrap registers AbCip/AbLegacy/FOCAS/Galaxy/Modbus/S7/TwinCAT factories) lives in src/Server/ZB.MOM.WW.OtOpcUa.Host/Drivers/."},
-    {"id": "F8", "subject": "Follow-up: VirtualTagActor engine wiring (compile expression, subscribe deps, publish result)", "status": "partial", "classification": "standard", "estMinutes": 30, "parallelizableWith": [], "blockedBy": [], "origin": "Self-review of Task 42 — VirtualTagEngine.Evaluate not called; DependencyValueChanged just buffers.", "shipped": "IVirtualTagEvaluator seam in Commons.Engines + NullVirtualTagEvaluator default. VirtualTagActor calls evaluator on DependencyValueChanged, dedupes unchanged results, emits EvaluationResult to parent, publishes ScriptLogEntry Warning to script-logs DPS topic on evaluator failure. Production binding to Core.VirtualTags.VirtualTagEngine still TODO (compile + ITagUpstreamSource subscribe) — split as F8b."},
+    {"id": "F8", "subject": "Follow-up: VirtualTagActor engine wiring (compile expression, subscribe deps, publish result)", "status": "partial", "classification": "standard", "estMinutes": 30, "parallelizableWith": [], "blockedBy": [], "origin": "Self-review of Task 42 — VirtualTagEngine.Evaluate not called; DependencyValueChanged just buffers.", "shipped": "(1) IVirtualTagEvaluator seam + NullVirtualTagEvaluator default. VirtualTagActor calls evaluator on DependencyValueChanged, dedupes unchanged results, emits EvaluationResult to parent, publishes Warning ScriptLogEntry on failure. (2) DependencyMuxActor in Runtime fans out DriverInstanceActor.AttributeValuePublished from DriverHostActor through to interested VirtualTagActor subscribers. VirtualTagActor takes dependencyRefs + mux ActorRef in Props, registers interest in PreStart, unregisters in PostStop. WithOtOpcUaRuntimeActors spawns the mux + threads it into DriverHostActor. Production binding to Core.VirtualTags.VirtualTagEngine (expression compile + dep extraction) still TODO — split as F8b."},
     {"id": "F9", "subject": "Follow-up: ScriptedAlarmActor engine wiring + state persistence", "status": "partial", "classification": "standard", "estMinutes": 30, "parallelizableWith": [], "blockedBy": [], "origin": "Self-review of Task 43 — AlarmConditionService not called; PreRestart persistence to ScriptedAlarmState DB not wired; HistorianAdapter rows not emitted.", "shipped": "(1) IScriptedAlarmEvaluator seam + NullScriptedAlarmEvaluator default. ScriptedAlarmActor takes AlarmConfig (id/name/path/severity/predicate), evaluates on DependencyValueChanged, publishes AlarmTransitionEvent + ScriptLogEntry on every transition. (2) IAlarmActorStateStore seam in Commons.Engines + NullAlarmActorStateStore default + EfAlarmActorStateStore production adapter over the ScriptedAlarmState entity. ScriptedAlarmActor PreStart loads + restores; every Transition fires a fire-and-forget save with lastAckUser. Predicate binding to Core.ScriptedAlarms.ScriptedAlarmEngine still TODO — split as F9b."},
     {"id": "F10", "subject": "Follow-up: OpcUaPublishActor SDK integration (address-space writes + ServiceLevel + RebuildAddressSpace)", "status": "partial", "classification": "high-risk", "estMinutes": 60, "parallelizableWith": [], "blockedBy": [47], "origin": "Self-review of Task 44 — SDK calls stubbed; counters only. Wire after Phase 7 OpcUaServer extraction.", "shipped": "IOpcUaAddressSpaceSink + IServiceLevelPublisher seams in Commons.OpcUa with Null* defaults. OpcUaPublishActor routes AttributeValueUpdate/AlarmStateUpdate/RebuildAddressSpace to the sink, dedupes ServiceLevelChanged, subscribes to redundancy-state DPS topic, and maps per-local-node redundancy snapshot to a coarse ServiceLevel (Primary+leader=240, Primary=200, Secondary=100, Detached=0). Production binding to a real SDK NodeManager + Variable nodes still TODO — split as F10b. Task 60 still blocked on F10b."},
     {"id": "F11", "subject": "Follow-up: HistorianAdapterActor named-pipe IPC + SqliteStoreAndForwardSink wiring", "status": "completed", "classification": "standard", "estMinutes": 30, "parallelizableWith": [], "blockedBy": [], "commit": "6861381", "deviationNotes": "Reshaped HistorianAdapterActor around the existing IAlarmHistorianSink abstraction (alarm-event shape, not the original tag-history-row stub). Defaults to NullAlarmHistorianSink; production deployments wire SqliteStoreAndForwardSink + WonderwareHistorianClient via AddOtOpcUaRuntime overrides. Actor now exposes GetStatus returning HistorianSinkStatus for diagnostics. Named-pipe transport implementation lives unchanged in src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Wonderware.Client/WonderwareHistorianClient.cs — the actor is intentionally just a fire-and-forget bridge.", "origin": "Self-review of Task 45 — stub buffers in-memory; named-pipe + SQLite store-and-forward not wired."},