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.Host/Program.cs

@@ -160,7 +160,7 @@ try
         // which would let DI hand the instance back and bypass Grpc.AspNetCore's own activation
         // path (the shape that once hid a two-public-constructor defect until the rig caught it).
         // CentralControlGrpcService decodes each request onto the same in-process message the
-        // ClusterClient path carries and Asks CentralCommunicationActor — zero handler logic here.
+        // removed ClusterClient path used to carry, and Asks CentralCommunicationActor — zero handler logic here.
         builder.Services.AddGrpc(options =>
         {
             options.Interceptors.Add<CentralControlAuthInterceptor>();
@@ -638,7 +638,7 @@ try
         builder.Services.AddSingleton<ZB.MOM.WW.ScadaBridge.Communication.Grpc.SiteStreamGrpcServer>();
         // Site command plane (central→site) — the gRPC peer of SiteStreamGrpcServer. Both share
         // the h2c listener and the ControlPlaneAuthInterceptor PSK gate; both are readiness-gated
-        // (SetReady, below). Central still dials over ClusterClient until T1B.3.
+        // (SetReady, below).
         builder.Services.AddSingleton<ZB.MOM.WW.ScadaBridge.Communication.Grpc.SiteCommandGrpcService>();
 
         // Existing site service registrations (this is also where LocalDb and its