Evaluate AGENTS.md and skills with Codex

[RoyLee1224]

cc: @jason810496

Follow up on #69308 by adding Codex as an alternative runtime for evaluating AGENTS.md and skills through promptfoo's built-in Codex SDK provider.

Run the evaluation with Codex:

AGENT_RUNTIME=codex \
  prek run run-skill-eval --hook-stage manual --all-files

The evaluation completed all six cases with no provider errors. Four behavioral assertions passed and two existing ambiguous newsfragment cases failed.

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Was generative AI tooling used to co-author this PR?

• Yes gpt-5.6-sol

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• Read the Pull Request Guidelines for more information. Note: commit author/co-author name and email in commits become permanently public when merged.
• For fundamental code changes, an Airflow Improvement Proposal (AIP) is needed.
• When adding dependency, check compliance with the ASF 3rd Party License Policy.
• For significant user-facing changes create newsfragment: {pr_number}.significant.rst, in airflow-core/newsfragments. You can add this file in a follow-up commit after the PR is created so you know the PR number.

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Important

🛠️ Maintainer triage note for @RoyLee1224 · by @potiuk · 2026-07-28 16:32 UTC

Some review feedback from jason810496 is waiting on you:

• There are 5 unresolved review threads on this PR from jason810496.

The ball is in your court — you've been assigned to this PR. Push a fix or reply in each thread explaining why the feedback does not apply, then mark them resolved and ping the reviewer (jason810496) for a final look.

See the Pull Request quality criteria for how to fix each item. There is no rush.

Note: your branch is 225 commits behind main — please rebase and push again to get up-to-date CI results.

_{Automated triage — may be imperfect; a maintainer takes the next look. We use this two-stage triage process so maintainers' limited time goes to the conversation with you.}

[jason810496]

Thanks for adding the Codex support!

[jason810496]

LGTM after resolving the following comments, thanks.

[jason810496]

Thanks.