fix(repair): close active backend before rollback restore

Rollback cleanup was instantiating a fresh ChromaBackend, so the live backend that had opened the PersistentClient could keep file handles alive during restore. Close the active backend instance instead so rollback and CLI recovery can release Windows-safe locks before copying the backup back into place.

mempalace/repair.py

@@ -517,7 +517,7 @@ def rebuild_index(palace_path=None, confirm_truncation_ok: bool = False):
         if e.live_replaced and os.path.exists(backup_path):
             print(f"  Restoring from backup: {backup_path}")
             try:
-                _close_chroma_handles(palace_path)
+                _close_chroma_handles(palace_path, backend=backend)
                 _delete_collection_if_exists(backend, palace_path, COLLECTION_NAME)
                 shutil.copy2(backup_path, sqlite_path)
                 print("  Backup restored. Palace is back to pre-repair state.")
@@ -593,12 +593,18 @@ def status(palace_path=None) -> dict:
 # ---------------------------------------------------------------------------
 
 
-def _close_chroma_handles(palace_path: str) -> None:
-    """Drop ChromaBackend + chromadb singleton caches so OS mmap handles release."""
+def _close_chroma_handles(palace_path: str, backend: ChromaBackend | None = None) -> None:
+    """Drop ChromaBackend + chromadb singleton caches so OS mmap handles release.
+
+    When ``backend`` is provided, close the live instance so rollback/restore
+    releases the handles it was already using. Otherwise fall back to a
+    transient backend instance for the max-seq-id repair path.
+    """
     import gc
 
     try:
-        ChromaBackend().close_palace(palace_path)
+        closer = backend if backend is not None else ChromaBackend()
+        closer.close_palace(palace_path)
     except Exception:
         pass
     try: