fix(localdb): telemetry review fixes — meter naming, snapshot status, session-count Connected

Claude-Session: https://claude.ai/code/session_01BL2Vu1ESDQ9SCN4gVKkdts

ZB.MOM.WW.LocalDb/src/ZB.MOM.WW.LocalDb.Replication/Internal/OplogStore.cs

@@ -81,9 +81,12 @@ internal sealed class OplogStore(ILocalDb db, ReplicationOptions options, Func<D
 
     /// <summary>
     /// The unacked backlog read synchronously on a dedicated short-lived connection, for the
-    /// metric-observation callbacks (gauge scrape / status poll). Cheap enough at that frequency;
-    /// mirrors <see cref="GetOplogDepthAsync"/>'s query. May throw if the db is disposing — callers
-    /// on the observation path swallow and drop the sample.
+    /// metric-observation callbacks (gauge scrape / status poll); mirrors
+    /// <see cref="GetOplogDepthAsync"/>'s query. Deliberate tradeoff: synchronous I/O on the
+    /// metrics-collection thread is acceptable here because WAL-mode readers never block (or are
+    /// blocked by) writers, the COUNT is indexed-cheap, and the worst case is bounded by
+    /// <c>BusyTimeoutMs</c> — all at scrape frequency, not on any data path. May throw if the db
+    /// is disposing — callers on the observation path swallow and drop the sample.
     /// </summary>
     public long GetOplogDepthSync()
     {

ZB.MOM.WW.LocalDb/src/ZB.MOM.WW.LocalDb.Replication/Internal/SyncSession.cs

@@ -169,7 +169,8 @@ internal sealed class SyncSession
             if (SnapshotSender is null)
                 throw new NotSupportedException("snapshot required but no snapshot sender configured");
             var snapshotAsOfSeq = await SnapshotSender(dataSend, ct);
-            _metrics?.RecordSnapshot("sent");
+            _metrics?.RecordSnapshotSent();
+            _status?.SetLastSyncUtc(_utcNow());
             // The snapshot already carries every row state up to as-of; skipping the pump past it
             // avoids re-sending tail deltas the peer would only discard via LWW.
             if (snapshotAsOfSeq > _sentThruSeq)
@@ -275,7 +276,8 @@ internal sealed class SyncSession
                                 "Replication protocol error: SnapshotComplete with no active snapshot (missing SnapshotBegin).");
                         await SnapshotApplier!.OnCompleteAsync(msg.SnapshotComplete, ct);
                         _snapshotReceiving = false;
-                        _metrics?.RecordSnapshot("received");
+                        _metrics?.RecordSnapshotReceived();
+                        _status?.SetLastSyncUtc(_utcNow());
                         break;
                     default:
                         throw new InvalidOperationException(