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/Drivers/DriverFactoryBootstrap.cs

@@ -0,0 +1,55 @@
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Core.Hosting;
+
+namespace ZB.MOM.WW.OtOpcUa.Host.Drivers;
+
+/// <summary>
+///     Wires every cross-platform driver assembly's <c>Register(registry, loggerFactory)</c>
+///     extension into a single <see cref="DriverFactoryRegistry"/> singleton and binds the
+///     v2 <see cref="IDriverFactory"/> abstraction to a <see cref="DriverFactoryRegistryAdapter"/>
+///     over it. Replaces the F7 seam's <c>NullDriverFactory</c> default so deploys actually
+///     materialise real <see cref="IDriver"/> instances on driver-role nodes.
+///
+///     Skipped entirely on admin-only nodes — they never run drivers, so the registry doesn't
+///     need to exist (Program.cs guards via the <c>hasDriver</c> flag).
+/// </summary>
+public static class DriverFactoryBootstrap
+{
+    /// <summary>
+    ///     Register the cross-platform driver factories + bind <see cref="IDriverFactory"/>.
+    ///     Must be called BEFORE <c>services.AddAkka</c> so the runtime extension can resolve
+    ///     <see cref="IDriverFactory"/> from DI when spawning <c>DriverHostActor</c>.
+    /// </summary>
+    public static IServiceCollection AddOtOpcUaDriverFactories(this IServiceCollection services)
+    {
+        services.AddSingleton<DriverFactoryRegistry>(sp =>
+        {
+            var registry = new DriverFactoryRegistry();
+            var loggerFactory = sp.GetService<ILoggerFactory>();
+            Register(registry, loggerFactory);
+            return registry;
+        });
+        services.AddSingleton<IDriverFactory>(sp =>
+            new DriverFactoryRegistryAdapter(sp.GetRequiredService<DriverFactoryRegistry>()));
+        return services;
+    }
+
+    /// <summary>
+    ///     Invoke every cross-platform driver's <c>Register</c> extension. New driver assemblies
+    ///     get added here — one line per type. ShouldStub() in <c>DriverInstanceActor</c> still
+    ///     handles platform/role-dependent stubbing (e.g. Galaxy on macOS), so registering a
+    ///     factory here doesn't mean it always runs in production.
+    /// </summary>
+    private static void Register(DriverFactoryRegistry registry, ILoggerFactory? loggerFactory)
+    {
+        Driver.AbCip.AbCipDriverFactoryExtensions.Register(registry);
+        Driver.AbLegacy.AbLegacyDriverFactoryExtensions.Register(registry, loggerFactory);
+        Driver.FOCAS.FocasDriverFactoryExtensions.Register(registry);
+        Driver.Galaxy.GalaxyDriverFactoryExtensions.Register(registry, loggerFactory);
+        Driver.Modbus.ModbusDriverFactoryExtensions.Register(registry, loggerFactory);
+        Driver.S7.S7DriverFactoryExtensions.Register(registry);
+        Driver.TwinCAT.TwinCATDriverFactoryExtensions.Register(registry);
+    }
+}