release: publish harel-python to PyPI

[fruwe]

Package and publish harel-python to PyPI so other Python programs can pip install
and import harel.

Scope (one PR)

• Finalize distribution metadata in pyproject.toml (classifiers, urls, keywords;
  confirm the PyPI distribution name — harel if free, else a fallback — while keeping
  the import name harel).
• Add a tag-triggered release workflow (.github/workflows/release.yml) that builds the
  sdist + wheel and publishes via PyPI Trusted Publishing (OIDC); verify
  python -m build produces an importable wheel in CI.
• Perform the first publish (requires a PyPI token / trusted-publisher configured by
  the maintainer).

No spec change. Standalone.

[fruwe]

Packaging is done and merged (#17): distribution name harel-python (import name harel), cel-python moved to runtime deps, classifiers/keywords/urls + py.typed, and a tag-triggered Trusted-Publishing release workflow. python -m build → sdist + wheel that twine check passes and that installs/imports/runs in a clean venv.

The actual first publish to PyPI is intentionally postponed until the package is confirmed stable. Keeping this issue open to track it.

When ready, either:

• Trusted Publishing (no token): configure a PyPI pending publisher (project harel-python, owner fruwehq, repo harel-python, workflow release.yml, environment pypi), then push a v0.1.0 tag — release.yml publishes via OIDC; or
• Manual: python -m build && twine upload dist/* with a maintainer token.