Update the internal setup-node dependency to a Node 24-compatible version

[mkanetsuna]

Summary

codex-action currently uses a commit SHA corresponding to actions/setup-node@v4.4.0 in the Ensure Node.js available step in action.yml.

Relevant location:

• action.yml
• uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4.4.0

Because of this, workflows that use codex-action show GitHub Actions' Node.js 20 deprecation warning.

Example warning:

Node.js 20 actions are deprecated. The following actions are running on Node.js 20 and may not work as expected: actions/setup-node@49933ea

Proposed change

Update the internal actions/setup-node dependency used by codex-action to a Node 24-compatible version (v6 series) to remove the warning.

node-version: "20" should remain unchanged in this change.

References

• GitHub Changelog: Deprecation of Node 20 on GitHub Actions runners
  • https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/
• actions/setup-node@v4.0.1 action metadata
  • https://raw.githubusercontent.com/actions/setup-node/v4.0.1/action.yml
• actions/setup-node@v6 action metadata
  • https://raw.githubusercontent.com/actions/setup-node/v6/action.yml