Update docs deploy workflow actions for Node.js 24 runner compatibility

[Copilot]

The docs deployment workflow still used action major versions tied to Node.js 20, which now triggers deprecation warnings and upcoming runtime incompatibility on GitHub-hosted runners. This updates the workflow to Node.js 24-compatible action majors.

• Workflow updates (.github/workflows/docs-deploy.yml)

  • actions/checkout upgraded from v4 → v6
  • actions/setup-python upgraded from v5 → v6
  • actions/upload-pages-artifact upgraded from v3 → v5

• Scope

  • Limited to docs-deploy.yml; no behavior or logic changes outside action version bumps.

- uses: actions/checkout@v6
- uses: actions/setup-python@v6
- uses: actions/upload-pages-artifact@v5

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• api.mystmd.org
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node node /home/REDACTED/.local/lib/python3.12/site-packages/mystmd_py/myst.cjs build --html (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)