release: 0.3.1

[Par-python]

Bumps the version to 0.3.1 (pyproject.toml, entroscope/__version__) and dates the changelog entry.

Everything in this release is already on master via #9 (and the CI change in #8). The full notes are in CHANGELOG.md.

⚠️ Results change: a NaN or ±inf in the input now gives NaN instead of a plausible-looking number, and rolling is NaN for exactly the windows that contain it. Code that relied on a finite value for gappy input will now see NaN.

After merge: tag v0.3.1 on the merge commit (this triggers the PyPI publish workflow) and create the GitHub release.

Test plan

• python -m build produces entroscope-0.3.1 wheel + sdist; twine check passes
• Wheel metadata: version 0.3.1, Homepage github.com/Par-python/entroscope, extras sklearn, polars, reference, docs, dev
• Wheel contains the NaN fix (_core.nan_on_non_finite)
• CI green (required checks)

🤖 Generated with Claude Code