feat(properties): harden standalone properties lifecycle

- synchronize child appearance and hidden-window readiness
- serialize native Torrent mutations transactionally without double-encoded rows
- preserve native lifecycle markers and fence stale or duplicate actions
- remove the obsolete modal surface and ignore implementation_plan.md

src/index.css

@@ -643,11 +643,6 @@ html[data-list-density="relaxed"] {
     max-height: min(680px, 100%);
   }
 
-  .properties-modal {
-    max-width: 100%;
-    max-height: 100%;
-  }
-
   /* Add Download window */
   .add-download-modal {
     width: min(900px, 100%);