Update CI actions to Node 24 runtimes

[dd3ok]

Summary

• update actions/checkout from v4 to v7
• update actions/setup-python from v5 to v6

Why

The first post-merge main run passed but GitHub emitted a Node.js 20 deprecation annotation for both actions. The selected current major releases declare using: node24 in their official action metadata.

Official releases:

• https://github.com/actions/checkout/releases/tag/v7.0.0
• https://github.com/actions/setup-python/releases/tag/v6.3.0

Validation

• 166 local tests
• policy and release-ready metadata checks
• git diff --check
• GitHub CI will validate the workflow on this PR

[gemini-code-assist]

Note

Gemini is unable to generate a review for this pull request due to the file types involved not being currently supported.

[dd3ok]

Self-review completed on the exact one-file PR head.

No P0-P2 findings. The only changes are checkout@v4 → checkout@v7 and setup-python@v5 → setup-python@v6. Official release metadata was checked: current releases are checkout v7.0.0 and setup-python v6.3.0, and both action manifests use Node 24. Local 166-test, policy, release-ready metadata, and whitespace checks pass.