fix(localdb): adapter review fixes — deterministic pump teardown, always-hosted initiator, backoff clamp

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

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

@@ -10,6 +10,16 @@ namespace ZB.MOM.WW.LocalDb.Replication.Internal;
 /// </summary>
 internal static class SyncSessionFactory
 {
+    /// <summary>
+    /// The engine binds to <see cref="SqliteLocalDb"/> internals (NodeId, Clock, replicated-table
+    /// digests), so both adapters require the concrete type AddZbLocalDb registers behind ILocalDb.
+    /// </summary>
+    public static SqliteLocalDb RequireSqlite(ILocalDb db, string consumer) =>
+        db as SqliteLocalDb
+        ?? throw new InvalidOperationException(
+            $"{consumer} requires the ILocalDb registered by AddZbLocalDb (a {nameof(SqliteLocalDb)}); " +
+            $"got {db.GetType().FullName}.");
+
     public static SyncSession Create(SqliteLocalDb db, ReplicationOptions options, ILoggerFactory loggerFactory)
     {
         var store = new OplogStore(db, options);