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/Actors/SiteCommunicationActorTransportTests.cs

@@ -104,7 +104,7 @@ public class SiteCommunicationActorTransportTests : TestKit
         // The seam preserves the reply-routing the S&F layer depends on: when the transport
         // answers the captured replyTo with a Status.Failure (its transient-failure signal on a
         // non-OK status), that failure reaches the original sender — here the test actor — so the
-        // waiting Ask faults, exactly as it did on the ClusterClient path.
+        // waiting Ask faults, exactly as it did on the removed ClusterClient path.
         var transport = Substitute.For<ICentralTransport>();
         transport
             .When(t => t.SubmitNotification(Arg.Any<NotificationSubmit>(), Arg.Any<IActorRef>()))