`checksumdir` uses deprecated `pkg_resources`

```
/Users/pete/.local/share/uv/tools/calkit-python/lib/python3.12/site-packages/checksumdir/__init__.py:17: UserWarning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pkg_resources.html. The pkg_resources package is slated for removal as early as 2025-11-30. Refrain from using this package or pin to Setuptools<81.
import pkg_resources
```

See https://github.com/to-mc/checksumdir/issues/22