Upgrade GitHub Actions to Node.js 24 compatible versions

[jacalata]

Node.js 20 is deprecated on GitHub Actions runners. The following actions target Node.js 20 but are being forced to run on Node.js 24:

• actions/checkout@v4
• actions/setup-python@v5
• actions/upload-artifact@v4

These should be updated to versions that natively target Node.js 24.

See: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 14 days if no further activity occurs. If this is still relevant, please comment to keep it open.

[jacalata]

Closing — dependabot is configured for github-actions on a weekly schedule (.github/dependabot.yml) and will pick this up automatically once the upstream actions ship a release with the fix.