Update GitHub Actions runtime

[yiheng8023]

Summary

• update official GitHub Actions to current v7 runtime lines
• verify the public template workflow cannot silently regress to deprecated action majors

Official release evidence

• actions/checkout v7.0.1 (2026-07-20)
• actions/setup-python v7.0.0 (2026-07-20)

Verification

• python -B scripts/verify.py
• git diff --check

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Validate active workflow steps instead of raw substrings

If either action is downgraded while the v7 reference remains in a YAML comment, an unused step, or a longer string such as actions/checkout@v70, this check still passes, so it does not provide the promised regression protection. Parse the workflow steps or match complete active uses: entries, and reject stale versions of these actions.

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