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/Grpc/GrpcCentralTransport.cs

@@ -11,8 +11,8 @@ using AkkaStatus = Akka.Actor.Status;
 namespace ZB.MOM.WW.ScadaBridge.Communication.Grpc;
 
 /// <summary>
-/// The <see cref="ICentralTransport"/> that carries the seven site→central sends over gRPC — the
-/// migration target for the Akka <c>ClusterClient</c> path. Each method encodes the message with
+/// The <see cref="ICentralTransport"/> that carries the seven site→central sends over gRPC —
+/// the replacement for the removed Akka <c>ClusterClient</c> path. Each method encodes the message with
 /// <see cref="CentralControlDtoMapper"/>, dials <c>CentralControlService</c> through the sticky
 /// <see cref="CentralChannelProvider"/>, and delivers the decoded reply (or a transient-failure
 /// signal) to the waiting Ask.