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/Grpc/DebugStreamBridgeActorTests.cs

@@ -293,7 +293,7 @@ public class DebugStreamBridgeActorTests : TestKit
 
         ctx.BridgeActor.Tell(new StopDebugStream());
 
-        // Should send ClusterClient unsubscribe
+        // Should send the site-addressed unsubscribe
         var envelope = ctx.CommProbe.ExpectMsg<SiteEnvelope>();
         Assert.IsType<UnsubscribeDebugViewRequest>(envelope.Message);