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.IntegrationTests/AuditLog/SiteAuditPushFlowTests.cs

@@ -24,14 +24,14 @@ namespace ZB.MOM.WW.ScadaBridge.IntegrationTests.AuditLog;
 
 /// <summary>
 /// End-to-end integration test for the Audit Log (#23) site→central push path
-/// introduced by the "real ClusterClient-based site audit push client" follow-up.
+/// introduced by the "real site audit push client" follow-up.
 /// </summary>
 /// <remarks>
 /// <para>
 /// Exercises the full production chain in one actor system: the real
 /// <see cref="SqliteAuditWriter"/> site SQLite hot-path, the real
 /// <see cref="SiteAuditTelemetryActor"/> drain loop, the real
-/// <see cref="ClusterClientSiteAuditClient"/>, the real
+/// <see cref="SiteCommunicationAuditClient"/>, the real
 /// <see cref="SiteCommunicationActor"/> forward, the real
 /// <see cref="CentralCommunicationActor"/> routing, and the real
 /// <c>AuditLogIngestActor</c> ingest — only the cross-cluster gRPC transport itself is
@@ -180,7 +180,7 @@ public class SiteAuditPushFlowTests : TestKit
             new BridgeCentralTransport(centralCommActor))));
 
         // The production site audit push client — the unit under integration.
-        var auditClient = new ClusterClientSiteAuditClient(
+        var auditClient = new SiteCommunicationAuditClient(
             siteCommActor, TimeSpan.FromSeconds(5));
 
         // Real SiteAuditTelemetryActor drains the writer's Pending queue and