Publish NeMo Gym to PyPI

[cwing-nvidia]

Summary

Set up PyPI publishing so users can install NeMo Gym via pip install nemo-gym.

Requirements

• [ ] Create PyPI project for nemo-gym
• [ ] Configure trusted publishing via GitHub Actions (preferred over API tokens)
• [ ] Add release workflow (.github/workflows/publish.yml)
• [ ] Test with TestPyPI before production release
• [ ] Document release process

Context

• Package metadata is already configured in pyproject.toml
• Version is managed in nemo_gym/package_info.py
• Build system: setuptools with python -m build

References

• PyPI Trusted Publishers
• gh-action-pypi-publish