feat(runtime,host): close F7 — driver subscribe + write paths + Host DI

Three pieces landed in one batch, closing F7-residual + Host DI #106:

Runtime/DriverInstanceActor:
  - Subscribe / Unsubscribe message contracts; the Connected state
    handles them via IDriver.ISubscribable. On every OnDataChange
    event the actor publishes AttributeValuePublished to its parent
    (DriverHostActor → OpcUaPublishActor). OPC UA StatusCode is
    mapped to the 3-state OpcUaQuality enum via severity bits
    (00=Good, 01=Uncertain, 10/11=Bad).
  - DetachSubscription tears the handler off the driver on
    DisconnectObserved, Unsubscribe, and PostStop so a stale handler
    never pushes to a dead actor.
  - WriteAttribute now dispatches IWritable.WriteAsync (batch of one)
    with a 5s CancellationTokenSource; status-code propagated to
    WriteAttributeResult on non-Good results.

Host:
  - New ProjectReferences to Core + every cross-platform driver
    assembly (AbCip/AbLegacy/FOCAS/Galaxy/Modbus/S7/TwinCAT).
    Galaxy is net10 (gRPC client to mxaccessgw); the COM-bound net48
    Wonderware Historian driver stays out of the Host's reference
    closure — its .Client gRPC wrapper is what binds for historian
    needs.
  - New DriverFactoryBootstrap.AddOtOpcUaDriverFactories() registers
    a singleton DriverFactoryRegistry, invokes each driver's
    Register(registry, loggerFactory), and binds IDriverFactory to
    DriverFactoryRegistryAdapter. Replaces the F7 NullDriverFactory
    default so deploys actually materialise real IDriver instances
    on driver-role nodes. ShouldStub() still gates per-platform
    behaviour at spawn time.
  - Program.cs wires AddOtOpcUaDriverFactories() before AddAkka so
    the runtime extension can resolve IDriverFactory from DI.

Tests: Runtime 46 -> 52 (+6):
- Write returns success when StatusCode = Good
- Write propagates non-Good status code in failure Reason
- Subscribe forwards OnDataChange to parent as AttributeValuePublished
- Quality translation: Uncertain (0x40...) and Bad (0x80...)
- Subscribe against non-ISubscribable returns failure
- DisconnectObserved detaches handler so late events are dropped

All 6 v2 test suites green: 152 tests passing.

Closes F7. F7-residual sub-tasks #110 (subscribe) and #111 (write)
both shipped. Host DI binding #106 shipped.

src/Server/ZB.MOM.WW.OtOpcUa.Host/Program.cs

@@ -8,6 +8,7 @@ using ZB.MOM.WW.OtOpcUa.Cluster;
 using ZB.MOM.WW.OtOpcUa.Configuration;
 using ZB.MOM.WW.OtOpcUa.ControlPlane;
 using ZB.MOM.WW.OtOpcUa.Host;
+using ZB.MOM.WW.OtOpcUa.Host.Drivers;
 using ZB.MOM.WW.OtOpcUa.Host.Health;
 using ZB.MOM.WW.OtOpcUa.Runtime;
 using ZB.MOM.WW.OtOpcUa.Security;
@@ -40,7 +41,13 @@ builder.Services.AddOtOpcUaConfigDb(builder.Configuration);
 builder.Services.AddOtOpcUaCluster(builder.Configuration);
 
 if (hasDriver)
+{
     builder.Services.AddOtOpcUaRuntime();
+    // Bind every cross-platform driver factory before AddAkka resolves IDriverFactory — replaces
+    // the F7-default NullDriverFactory with a real DriverFactoryRegistryAdapter so DriverHostActor
+    // can materialise real IDriver instances on deploy.
+    builder.Services.AddOtOpcUaDriverFactories();
+}
 
 // Akka cluster bootstrap. Role-specific singletons are registered on the AkkaConfigurationBuilder
 // from inside the configurator lambda. AddAkka spins the ActorSystem at host start.