feat(mesh): Grpc mode value + validation

src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/AdminOperations/AdminOperationsActor.cs

@@ -88,8 +88,12 @@ public sealed class AdminOperationsActor : ReceiveActor
     /// </summary>
     /// <remarks>
     ///     The fallback keeps ~12 existing tests (and any node wired before per-cluster mesh Phase 2)
-    ///     on exactly the pre-Phase-2 behaviour. It is not a permanent seam: Phase 6 deletes it along
-    ///     with the DistributedPubSub branch and the single mesh.
+    ///     on exactly the pre-Phase-2 behaviour. The DistributedPubSub branch behind it is
+    ///     <b>retained</b>, not scheduled for deletion — an earlier note here promised Phase 6 would
+    ///     remove it, which was deliberately reversed (<c>docs/Configuration.md</c> § "The compiled
+    ///     transport-mode defaults were deliberately NOT flipped"): DPS is still the correct and
+    ///     default transport for a single-mesh topology. What is being replaced is the ClusterClient
+    ///     branch, by gRPC.
     /// </remarks>
     /// <param name="topic">The legacy DistributedPubSub topic.</param>
     /// <param name="message">The command.</param>

src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/Coordinators/ConfigPublishCoordinator.cs

@@ -68,8 +68,11 @@ public sealed class ConfigPublishCoordinator : ReceiveActor, IWithTimers
     /// </summary>
     /// <remarks>
     ///     Null in tests and on any node wired before Phase 2, where the fallback reproduces the
-    ///     pre-Phase-2 behaviour exactly. The fallback is not a permanent seam — Phase 6 deletes it
-    ///     along with the DistributedPubSub branch and the single mesh.
+    ///     pre-Phase-2 behaviour exactly. The DistributedPubSub branch behind it is <b>retained</b>,
+    ///     not scheduled for deletion — an earlier note here promised Phase 6 would remove it, which
+    ///     was deliberately reversed (<c>docs/Configuration.md</c> § "The compiled transport-mode
+    ///     defaults were deliberately NOT flipped"): DPS is still the correct and default transport
+    ///     for a single-mesh topology. What is being replaced is the ClusterClient branch, by gRPC.
     /// </remarks>
     private readonly IActorRef? _meshRouter;
     private readonly ILoggingAdapter _log = Context.GetLogger();