Run GitHub Actions on Node.js 24

[KimGLee]

Closes #121

Summary

• upgrade all required and deep-verification checkout steps to actions/checkout v7.0.1
• upgrade all Python setup steps to actions/setup-python v7.0.0
• pin both actions to their complete official release commit SHAs
• retain readable version comments, the Python 3.10/3.14 matrix, and the stable ci-required context

Both pinned release manifests declare node24. Checkout v7's fork protection changes do not alter these workflows because they use pull_request, push, and workflow_dispatch, not pull_request_target or workflow_run. Setup-python v7's removed pip-install input is not used here.

Validation

• official release tags, complete commit SHAs, and action.yml Node.js 24 runtime declarations verified
• no checkout v4 or setup-python v5 references remain
• workflow YAML parsing passed
• Actionlint v1.7.12 passed for both workflows
• make check passed
• diff and whitespace checks passed
• impact planner resolves this CI-authority change to full Python 3.10/3.14 verification

Remote CI must complete without the previous Node.js 20 deprecation annotation before merge.

Scope

Only .github/workflows/verify.yml and .github/workflows/deep-verify.yml change. Test selection, project Python support, permissions, triggers, and deep-verification behavior are unchanged.