Prepare package releases

[fazpu]

Summary

• Add a tag-triggered PyPI release workflow matching team-harness release automation
• Build distributions with uv, run strict twine checks, publish via PyPI trusted publishing, and create a GitHub Release
• Relax Python package metadata to require >=3.12 without an upper bound, and update uv.lock accordingly

Validation

• uv build
• uv run --with twine twine check --strict dist/*
• uv run ruff check src/
• uv run ruff format --check src/
• uv run pyright src/ --pythonversion 3.13
• uv run pytest src/tests/ -v --tb=short