feat(hosts): driver diagnostics channel on /hosts, S7 negotiated PDU size first (#640)

Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe

src/Server/ZB.MOM.WW.OtOpcUa.Runtime/Drivers/AkkaDriverHealthPublisher.cs

@@ -38,7 +38,8 @@ public sealed class AkkaDriverHealthPublisher : IDriverHealthPublisher
         DateTime? rediscoveryNeededUtc = null,
         string? rediscoveryReason = null,
         IReadOnlyList<HostConnectivityStatus>? hostStatuses = null,
-        SkippedTagReport? skippedTags = null)
+        SkippedTagReport? skippedTags = null,
+        IReadOnlyDictionary<string, string>? diagnostics = null)
     {
         var msg = new DriverHealthChanged(
             clusterId,
@@ -51,7 +52,8 @@ public sealed class AkkaDriverHealthPublisher : IDriverHealthPublisher
             rediscoveryNeededUtc,
             rediscoveryReason,
             hostStatuses,
-            skippedTags);
+            skippedTags,
+            diagnostics);
         DistributedPubSub.Get(_system).Mediator.Tell(new Publish(TopicName, msg));
         // Phase 5: fan the same snapshot into the node-local live-telemetry hub (no-op until a gRPC
         // client subscribes). The DPS publish above is unchanged — the hub is a strictly additive tap.