Opt GitHub Actions into Node 24

[fazpu]

Summary

• opt CI and release workflows into GitHub's Node 24 JavaScript action runtime
• avoids the Node 20 deprecation warning emitted by checkout, artifact, and setup-uv actions

Validation

• git diff --check
• uv run python -c "import yaml, pathlib; [yaml.safe_load(p.read_text()) for p in pathlib.Path('.github/workflows').glob('*.yml')]; print('workflow yaml ok')"