pypackages: Reducto's private Python package index.

Install (keys are minted at https://pypackages-internal.reducto.ai):
  pip install --index-url https://__token__:$PYPACKAGES_KEY@pypackages.reducto.ai/simple/ <package>
  uv pip install --index-url https://__token__:$PYPACKAGES_KEY@pypackages.reducto.ai/simple/ <package>

Names that are not hosted here redirect to PyPI, so one --index-url covers every dependency.

Upload (needs a write key):
  twine upload --repository-url https://pypackages.reducto.ai/legacy/ -u __token__ -p $PYPACKAGES_KEY dist/*
  uv publish --publish-url https://pypackages.reducto.ai/legacy/ -u __token__ -p $PYPACKAGES_KEY