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.SiteRuntime/Scripts/ScriptRuntimeContext.cs

@@ -74,7 +74,7 @@ public class ScriptRuntimeContext
 
     /// <summary>
     /// Notification Outbox: the site communication actor that <c>Notify.Status</c>
-    /// queries central through (via the ClusterClient command/control transport).
+    /// queries central through (via the gRPC command/control transport).
     /// </summary>
     private readonly ICanTell? _siteCommunicationActor;
 
@@ -175,7 +175,7 @@ public class ScriptRuntimeContext
     /// <param name="externalSystemClient">Optional client for external system API calls.</param>
     /// <param name="databaseGateway">Optional gateway for database connection and cached write access.</param>
     /// <param name="storeAndForward">Optional store-and-forward service for notification delivery.</param>
-    /// <param name="siteCommunicationActor">Optional actor for site-to-central communication (ClusterClient).</param>
+    /// <param name="siteCommunicationActor">Optional actor for site-to-central communication.</param>
     /// <param name="siteId">Identifier of the site where this instance is running.</param>
     /// <param name="sourceScript">Optional name of the source script for audit trail identification.</param>
     /// <param name="auditWriter">Optional writer for audit log entries.</param>