Add type hints to public functions in pystore/utils.py

[ranaroussi]

Goal

The public utility functions in pystore/utils.py currently lack PEP 484 type annotations. Add type hints to all public functions in the file.

Acceptance criteria

• Add type annotations to the parameters and return types of all public functions in pystore/utils.py:
  • read_csv(urlpath, *args, **kwargs)
  • datetime_to_int64(df)
  • subdirs(d)
  • path_exists(path)
  • read_metadata(path)
  • write_metadata(path, metadata={})
  • make_path(*args)
  • get_path(*args)
  • set_path(path)
  • list_stores()
  • delete_store(store)
  • delete_stores()
  • set_client(scheduler=None)
  • get_client()
  • set_partition_size(size=None)
  • get_partition_size()
  • configure_logging(level=logging.INFO, format_string=None)
• Use pathlib.Path for path-typed args/returns where appropriate.
• Use pd.DataFrame (or dd.DataFrame for Dask) for dataframe types.
• Use Optional[X], Union[X, Y], Dict, List, Set from typing as needed (Python 3.7-compatible).
• Add a from typing import ... import line near the top of the file.
• Function bodies remain unchanged — annotations only.

Out of scope

• Type hints on private functions (anything starting with _)
• Refactoring or behavior changes
• Other files in the package

Verification

• python -c "import pystore.utils; help(pystore.utils.set_path)" should show typed signature
• Existing tests still pass: pytest tests/
• Optional: mypy pystore/utils.py should not introduce regressions (it may already report unrelated issues — those are not part of this task)