Document the PyPI release flow and make built artifacts PyPI-valid

[Copilot]

OpenCAD referenced PyPI installation, but the repository did not explain how to publish a release. This PR adds a concrete PyPI release path and aligns packaging metadata so generated artifacts are accepted by the current upload toolchain.

• Release documentation

  • Added RELEASING.md with the repository-native release flow:
    • update version in pyproject.toml
    • build with python -m build
    • validate with python -m twine check dist/*
    • upload to PyPI or TestPyPI
    • tag the released version
  • Linked the new guide from README.md so the release path is discoverable from the main docs entrypoint.

• Packaging compatibility

  • Updated pyproject.toml build requirements to pin setuptools to a PyPI-compatible range for this project’s current metadata shape.
  • Adjusted license metadata so built wheels/sdists validate cleanly with twine check while still carrying the project license in release artifacts.

• Repository hygiene

  • Added dist/ to .gitignore to avoid committing generated release artifacts.

Example release flow:

python -m pip install -U build twine
python -m build
python -m twine check dist/*
python -m twine upload dist/*
git tag vX.Y.Z
git push origin vX.Y.Z

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• packaging.python.org
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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