fix(utils): allow any JSON payload in write_json - #3993 (#4217)

* fix(utils): allow any JSON payload in write_json

The dict-only type stub blocked lists/scalars callers already dump.
Accept Any, set utf-8 encoding, and cover list roundtrip.

* fix(utils): json type

---------

Co-authored-by: Bartok9 <danielrpike9@gmail.com>

src/lerobot/utils/io_utils.py

@@ -32,21 +32,21 @@ def load_json(fpath: Path) -> Any:
     Returns:
         Any: The data loaded from the JSON file.
     """
-    with open(fpath) as f:
+    with open(fpath, encoding="utf-8") as f:
         return json.load(f)
 
 
-def write_json(data: dict, fpath: Path) -> None:
+def write_json(data: JsonLike, fpath: Path) -> None:
-    """Write data to a JSON file.
+    """Write JSON-serializable data to a file.
 
     Creates parent directories if they don't exist.
 
     Args:
-        data (dict): The dictionary to write.
+        data: JSON-serializable data to write.
         fpath (Path): The path to the output JSON file.
     """
     fpath.parent.mkdir(exist_ok=True, parents=True)
-    with open(fpath, "w") as f:
+    with open(fpath, "w", encoding="utf-8") as f:
         json.dump(data, f, indent=4, ensure_ascii=False)