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.Communication/CentralControlGrpc/CentralControlGrpc.cs

@@ -13,7 +13,7 @@ namespace ZB.MOM.WW.ScadaBridge.Communication.Grpc {
   ///
   /// Direction: SITE is the client, CENTRAL is the server — the inverse of
   /// SiteStreamService, where central dials the site. That asymmetry is deliberate
-  /// and mirrors the direction the Akka ClusterClient traffic flows today: these
+  /// and mirrors the direction the Akka ClusterClient traffic used to flow: these
   /// seven calls are exactly the seven messages SiteCommunicationActor sends to
   /// /user/central-communication.
   ///