test: fold the last Windows path and label assumptions

Second pass over the informational Windows job (91 failures -> 11 -> 0):

* `_identity`/`_fold` now wrap the assertions my first sweep skipped: the
  parenthesised and multi-line ones, and the ones whose token list was
  incomplete (`base_models_roots`, `embeddings_roots`).
* The reconciler's `current_name` and `active_roots` carry the drive-prefixed
  label on Windows ("C: loras"), so the last direct comparison goes through
  `_root_label_names` too.
* `open_settings_location` reveals the settings *file* with
  `explorer /select,` on Windows instead of opening the containing folder, so
  that test asserts the platform's call instead of the POSIX one.
* Three more expectations are written in the business form the code returns
  (metadata payload, extracted download paths, hydrated preview URL).

tests/utils/test_metadata_manager.py

@@ -60,7 +60,7 @@ async def test_load_metadata_payload_restores_file_facts_when_sidecar_missing(
     payload = await MetadataManager.load_metadata_payload(str(model_path))
 
     stat_result = model_path.stat()
-    assert payload["file_path"] == str(model_path)
+    assert payload["file_path"] == str(model_path).replace(os.sep, "/")
     assert payload["file_name"] == "MyModel"
     assert payload["size"] == stat_result.st_size
     assert payload["modified"] == stat_result.st_mtime