don't put checkpoint files inside namespace directories.

src/wikiq/__init__.py

@@ -322,7 +322,7 @@ class WikiqParser:
         """Open checkpoint file for writing. Keeps file open for performance."""
         if not self.output_parquet or output_file == sys.stdout.buffer:
             return
-        checkpoint_path = get_checkpoint_path(output_file)
+        checkpoint_path = get_checkpoint_path(output_file, self.partition_namespaces)
         Path(checkpoint_path).parent.mkdir(parents=True, exist_ok=True)
         self.checkpoint_file = open(checkpoint_path, 'w')
         print(f"Checkpoint file opened: {checkpoint_path}", file=sys.stderr)