ci: add trusted PyPI publishing

[halfaipg]

Summary

• publish grid-sdk only from a non-prerelease GitHub Release with an exact version tag
• use PyPI trusted publishing via GitHub OIDC and the protected pypi environment
• test the built wheel, pin release tooling/actions, and modernize MIT license metadata
• document the initial-publication state accurately

Verification

• wheel and sdist build successfully
• twine check passes
• pytest tests/ -v (17 passed)
• actionlint 1.7.12
• Gitleaks tracked diff and complete reachable history