refactor(comm): retire ClusterClient naming after the gRPC cutover

Phase 4 of the ClusterClient -> gRPC migration deleted the Akka transports
but left the naming behind: `ClusterClientSiteAuditClient` was transport-
agnostic and worked unchanged, so it survived the deletion under a name
that now describes a transport the repo no longer has. Same for a scatter
of doc-comments still framing gRPC as "the new transport" beside an Akka
one that is gone.

Renames it to `SiteCommunicationAuditClient` (and its test file) and
rewrites the stale comments to describe the single transport that exists.
Also tightens CLAUDE.md: drops the self-describing directory listing and
the 27-component enumeration in favour of the non-obvious parts only.

Behaviour-neutral: names and prose only. Recorded as the Phase 4
follow-up in docs/plans/2026-07-22-clusterclient-to-grpc-plan.md.

src/ZB.MOM.WW.ScadaBridge.StoreAndForward/NotificationForwarder.cs

@@ -26,10 +26,10 @@ namespace ZB.MOM.WW.ScadaBridge.StoreAndForward;
 ///   for operator forensics.</description></item>
 /// </list>
 ///
-/// The forward travels over the ClusterClient command/control transport: the handler
+/// The forward travels over the gRPC command/control transport: the handler
 /// <see cref="ActorRefImplicitSenderExtensions.Ask{T}(ICanTell, object, TimeSpan?)">Asks</see>
 /// the site communication actor, which wraps the message in a
-/// <c>ClusterClient.Send("/user/central-communication", …)</c> and routes central's
+/// <c>SubmitNotification</c> call on <c>CentralControlService</c> and routes central's
 /// reply straight back to this Ask.
 /// </summary>
 public sealed class NotificationForwarder
@@ -45,7 +45,7 @@ public sealed class NotificationForwarder
     /// </summary>
     /// <param name="siteCommunicationActor">
     /// The site communication actor. It forwards a <see cref="NotificationSubmit"/> to
-    /// central via the registered ClusterClient and replies with the
+    /// central over the site's central transport and replies with the
     /// <see cref="NotificationSubmitAck"/>.
     /// </param>
     /// <param name="sourceSiteId">This site's identifier, stamped on every submit.</param>