Resolve all 46 low-severity architecture review findings

src/ZB.MOM.WW.ScadaBridge.Communication/Grpc/CentralControlGrpcService.cs

@@ -39,17 +39,13 @@ namespace ZB.MOM.WW.ScadaBridge.Communication.Grpc;
 /// <see cref="SiteStreamGrpcServer.AuditIngestAskTimeout"/>, so the inner Ask expired at the same
 /// instant as the outer one and could only add latency plus a
 /// <see cref="Akka.Actor.Status.Failure"/> repackaging. The proxy now arrives through
-/// <see cref="SetAuditIngestActor"/>, exactly as <see cref="SiteStreamGrpcServer"/> has always
-/// taken it, and the relay handlers were deleted.
+/// <see cref="SetAuditIngestActor"/>; the redundant actor relay handlers were deleted.
 /// </para>
 /// <para>
-/// <b>Fault semantics deliberately differ from <see cref="SiteStreamGrpcServer"/>'s ingest
-/// RPCs.</b> That server answers a failed audit ingest with an EMPTY <c>IngestAck</c>; this one
-/// fails the call with a non-OK status. Both leave the site's rows <c>Pending</c> for the next
-/// drain, so the outcome is the same — but this service replaced the ClusterClient path, whose
-/// documented behaviour was to propagate the fault, and preserving that keeps a lost batch
-/// visible as a failure rather than as a successful call that acked nothing. A proxy that has
-/// not been handed over yet is NOT a fault and still answers with an empty ack.
+/// <b>Fault semantics.</b> Failed central ingest returns a non-OK status, leaving the site's
+/// rows Pending and making a lost batch visible to the next drain. A proxy not handed over
+/// yet returns an empty ack. The legacy SiteStreamService ingest methods are retired and
+/// always return Unimplemented; they are not an alternate ingestion path.
 /// </para>
 /// <para>
 /// <b>Status mapping, and why it is not uniform.</b> A site transport may safely re-send a call
@@ -126,9 +122,7 @@ public sealed class CentralControlGrpcService : CentralControlService.CentralCon
 
     /// <summary>
     /// Hands the central <c>AuditLogIngestActor</c> singleton proxy to the service so the two
-    /// ingest RPCs can Ask it DIRECTLY. Mirrors
-    /// <see cref="SiteStreamGrpcServer.SetAuditIngestActor"/> — the site-stream server has always
-    /// dispatched straight to the singleton, and this service now matches it.
+    /// ingest RPCs can Ask it directly. SiteStreamService retains only Unimplemented wire stubs.
     /// </summary>
     /// <remarks>
     /// Removing the <c>CentralCommunicationActor</c> relay removes an actor hop, a second Ask,