feat(runtime): WithOtOpcUaRuntimeActors extension for driver-role node startup (F19)

Mirrors WithOtOpcUaControlPlaneSingletons for the driver role. Spawns
DriverHostActor + DbHealthProbeActor on the host's ActorSystem and
registers both under marker keys. Host's Program.cs now calls it when
the node carries the driver role, so driver-only and admin+driver
deployments both auto-bootstrap the per-node actors.

Integration test covers the registration round-trip via Microsoft.Extensions.Hosting
+ Akka.Hosting AddAkka.

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

@@ -8,6 +8,7 @@ using ZB.MOM.WW.OtOpcUa.Configuration;
 using ZB.MOM.WW.OtOpcUa.ControlPlane;
 using ZB.MOM.WW.OtOpcUa.Host;
 using ZB.MOM.WW.OtOpcUa.Host.Health;
+using ZB.MOM.WW.OtOpcUa.Runtime;
 using ZB.MOM.WW.OtOpcUa.Security;
 using ZB.MOM.WW.OtOpcUa.Security.Endpoints;
 
@@ -43,10 +44,8 @@ builder.Services.AddAkka("otopcua", (ab, _) =>
 {
     if (hasAdmin)
         ab.WithOtOpcUaControlPlaneSingletons();
-    // Driver-role startup (DriverHostActor spawn + child probes) is wired in F19 once a
-    // RuntimeStartup contract is added — the actor itself exists (Phase 6), the registration
-    // extension does not yet. Without it, driver-role nodes still join the cluster and serve
-    // health/redundancy traffic but won't auto-spawn DriverHostActor.
+    if (hasDriver)
+        ab.WithOtOpcUaRuntimeActors();
 });
 
 if (hasAdmin)

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

@@ -0,0 +1,57 @@
+using Akka.Actor;
+using Akka.Hosting;
+using Microsoft.EntityFrameworkCore;
+using ZB.MOM.WW.OtOpcUa.Commons.Interfaces;
+using ZB.MOM.WW.OtOpcUa.Configuration;
+using ZB.MOM.WW.OtOpcUa.Runtime.Drivers;
+using ZB.MOM.WW.OtOpcUa.Runtime.Health;
+
+namespace ZB.MOM.WW.OtOpcUa.Runtime;
+
+public static class ServiceCollectionExtensions
+{
+    public const string DriverRole = "driver";
+
+    public const string DriverHostActorName = "driver-host";
+    public const string DbHealthProbeActorName = "db-health";
+
+    /// <summary>
+    /// Spawns the per-node driver-role actors on the host's <see cref="ActorSystem"/>:
+    /// <see cref="DriverHostActor"/> (one per node) and <see cref="DbHealthProbeActor"/>
+    /// (consumed by the health endpoint + redundancy calc).
+    ///
+    /// Mirror of <c>WithOtOpcUaControlPlaneSingletons</c> for the driver role. Both must
+    /// be registered on the same <see cref="AkkaConfigurationBuilder"/> as the cluster
+    /// bootstrap so the actors share the host's ActorSystem.
+    ///
+    /// Wire from the fused Host's Program.cs when the node carries the <c>driver</c> role:
+    /// <code>
+    /// if (hasDriver)
+    ///     ab.WithOtOpcUaRuntimeActors();
+    /// </code>
+    /// </summary>
+    public static AkkaConfigurationBuilder WithOtOpcUaRuntimeActors(this AkkaConfigurationBuilder builder)
+    {
+        builder.WithActors((system, registry, resolver) =>
+        {
+            var dbFactory = resolver.GetService<IDbContextFactory<OtOpcUaConfigDbContext>>();
+            var roleInfo = resolver.GetService<IClusterRoleInfo>();
+
+            var dbHealth = system.ActorOf(
+                DbHealthProbeActor.Props(dbFactory),
+                DbHealthProbeActorName);
+            registry.Register<DbHealthProbeActorKey>(dbHealth);
+
+            var driverHost = system.ActorOf(
+                DriverHostActor.Props(dbFactory, roleInfo.LocalNode),
+                DriverHostActorName);
+            registry.Register<DriverHostActorKey>(driverHost);
+        });
+
+        return builder;
+    }
+}
+
+/// <summary>Marker key types used by <c>Akka.Hosting</c> to resolve runtime actors from the registry.</summary>
+public sealed class DriverHostActorKey { }
+public sealed class DbHealthProbeActorKey { }