chore: add local python scripts/release.py command, drop tag-triggered workflow

[mishanefedov]

Summary

• Adds scripts/release.py: builds, publishes to PyPI (idempotent — skips if version already live), tags and pushes v<version>
• Deletes .github/workflows/release.yml (replaced by the local script)
• Adds ## Releasing section to README.md documenting the single command

Test plan

• python -c "import ast; ast.parse(open('scripts/release.py').read())" passes
• Verify python scripts/release.py with a real PyPI token before next version cut

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Summary by cubic

Adds a local release command: python scripts/release.py builds, uploads to PyPI, and tags v<version>. Removes the tag-triggered GitHub Actions release workflow and documents the steps in the README.

• New Features

  • Idempotent publish: skips if the version is already on PyPI.
  • Installs and uses build and twine automatically.
  • Creates and pushes v<version> git tag.

• Migration

  • Configure PyPI auth via ~/.pypirc or set TWINE_USERNAME=__token__ and TWINE_PASSWORD=....
  • Release with: python scripts/release.py (the v* tag workflow is removed).

^{Written for commit b230b39. Summary will update on new commits.}