feat(localdb): LWW applier (hlc+node_id tie-break, applying guard, dead-letter, atomic watermark)

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

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

@@ -0,0 +1,15 @@
+namespace ZB.MOM.WW.LocalDb.Replication;
+
+/// <summary>
+/// Thrown when a peer sends replication data whose schema this node cannot honor: an oplog entry
+/// for a table not registered for replication here. Unlike a poison entry (dead-lettered per-row),
+/// this is a protocol violation between the two nodes' registered schemas, so the whole batch is
+/// rejected before any of it is applied. Task 10 reuses it to fail the handshake closed.
+/// </summary>
+public sealed class LocalDbSchemaMismatchException : Exception
+{
+    public LocalDbSchemaMismatchException(string message) : base(message) { }
+
+    public LocalDbSchemaMismatchException(string message, Exception innerException)
+        : base(message, innerException) { }
+}