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.Commons/Messages/Management/ManagementCommandRegistry.cs

@@ -6,7 +6,7 @@ namespace ZB.MOM.WW.ScadaBridge.Commons.Messages.Management;
 /// Bidirectional name registry for management command records. The registry contains
 /// exactly the non-abstract <c>*Command</c> types declared in the
 /// <c>ZB.MOM.WW.ScadaBridge.Commons.Messages.Management</c> namespace; these are the commands that
-/// travel over the HTTP / ClusterClient management boundary.
+/// travel over the HTTP management boundary.
 /// </summary>
 /// <remarks>
 /// <see cref="Resolve"/> and <see cref="GetCommandName"/> are symmetric: