polish(localdb): final integration-review fixes — drift XML doc, trim core deps, metrics doc/encapsulation

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

ZB.MOM.WW.LocalDb/src/ZB.MOM.WW.LocalDb.Replication/LocalDbMetrics.cs

@@ -24,6 +24,7 @@ public sealed class LocalDbMetrics : IDisposable
     private readonly Func<DateTimeOffset> _utcNow;
     private bool _disposed;
 
+    /// <summary>Creates the meter and its instruments. <paramref name="utcNow"/> is a test seam for the lag gauge's clock; null uses <see cref="DateTimeOffset.UtcNow"/>.</summary>
     public LocalDbMetrics(Func<DateTimeOffset>? utcNow = null)
     {
         _utcNow = utcNow ?? (() => DateTimeOffset.UtcNow);
@@ -41,34 +42,40 @@ public sealed class LocalDbMetrics : IDisposable
     /// Supplies the current unacked oplog backlog for the <c>localdb.oplog.depth</c> gauge. Invoked
     /// only at collection time; a cheap synchronous SELECT is acceptable at that frequency.
     /// </summary>
-    public Func<long>? OplogDepthProvider { get; set; }
+    public Func<long>? OplogDepthProvider { get; internal set; }
 
     /// <summary>Supplies the last successful sync time for the <c>localdb.sync.lag.seconds</c> gauge; null means no sync yet, and the gauge then reports no measurement.</summary>
-    public Func<DateTimeOffset?>? LastSyncUtcProvider { get; set; }
+    public Func<DateTimeOffset?>? LastSyncUtcProvider { get; internal set; }
 
     /// <summary>The backing meter — exposed so a test <see cref="MeterListener"/> can filter by instance reference rather than the process-shared meter name.</summary>
     internal Meter Meter => _meter;
 
+    /// <summary>Adds <paramref name="count"/> rows applied from inbound delta batches to <c>localdb.sync.applied</c> (no-op when not positive).</summary>
     public void RecordApplied(long count)
     {
         if (count > 0) _applied.Add(count);
     }
 
+    /// <summary>Adds <paramref name="count"/> inbound rows that lost LWW to <c>localdb.sync.conflicts_discarded</c> (no-op when not positive).</summary>
     public void RecordConflictsDiscarded(long count)
     {
         if (count > 0) _conflictsDiscarded.Add(count);
     }
 
+    /// <summary>Adds <paramref name="count"/> poison / over-drift rows routed to the dead-letter table to <c>localdb.sync.dead_lettered</c> (no-op when not positive).</summary>
     public void RecordDeadLettered(long count)
     {
         if (count > 0) _deadLettered.Add(count);
     }
 
+    /// <summary>Increments <c>localdb.sync.reconnects</c> for one initiator reconnect attempt.</summary>
     public void RecordReconnect() => _reconnects.Add(1);
 
+    /// <summary>Increments <c>localdb.sync.snapshots</c> with <c>direction=sent</c> for one completed outbound snapshot.</summary>
     public void RecordSnapshotSent() =>
         _snapshots.Add(1, new KeyValuePair<string, object?>("direction", "sent"));
 
+    /// <summary>Increments <c>localdb.sync.snapshots</c> with <c>direction=received</c> for one completed inbound snapshot.</summary>
     public void RecordSnapshotReceived() =>
         _snapshots.Add(1, new KeyValuePair<string, object?>("direction", "received"));
 
@@ -99,6 +106,7 @@ public sealed class LocalDbMetrics : IDisposable
         return [new Measurement<double>(lag)];
     }
 
+    /// <summary>Disposes the backing meter; idempotent.</summary>
     public void Dispose()
     {
         if (_disposed)