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.

tests/ZB.MOM.WW.ScadaBridge.Communication.Tests/CentralCommunicationActorAuditTests.cs

@@ -15,10 +15,10 @@ using ZB.MOM.WW.ScadaBridge.Communication.Actors;
 namespace ZB.MOM.WW.ScadaBridge.Communication.Tests;
 
 /// <summary>
-/// Tests for the Audit Log (#23) site→central ClusterClient ingest routing on
-/// <see cref="CentralCommunicationActor"/>. A site ClusterClient delivers
+/// Tests for the Audit Log (#23) site→central ingest routing on
+/// <see cref="CentralCommunicationActor"/>. A site delivers
 /// <see cref="IngestAuditEventsCommand"/> / <see cref="IngestCachedTelemetryCommand"/>
-/// to the receptionist-registered actor, which forwards to the registered
+/// to the actor, which forwards to the registered
 /// <c>AuditLogIngestActor</c> proxy and routes the reply back to the site.
 /// Mirrors the NotificationSubmit / RegisterNotificationOutbox pattern.
 /// </summary>