[Feature]: Improve cron job support and UX for Codex gpt-5.4

[viiccwen]

Hello, I'm Vic! An Apache Software Foundation Contributor in apache/airflow & apache/mahout. 🙌
I think this project is pretty cool! So I made this feature patch haha.

Summary

This PR aligns cron job tooling and cron setup guidance with the existing Codex runtime capability for modern models, especially gpt-5.4.

The runtime already supports Codex cron execution through the shared task runner and model validation pipeline, but the user-facing cron tools and rule files were still biased toward older Codex model names and incomplete edit flows.

This change makes cron support for gpt-5.4 explicit and usable end-to-end.

What changed

1. Added missing cron edit functionality

tools/cron_tools/cron_edit.py now supports in-place execution override updates:

• --provider
• --model
• --reasoning-effort
• --cli-parameters

It also supports clearing those fields with:

• --clear-provider
• --clear-model
• --clear-reasoning-effort
• --clear-cli-parameters

This closes the gap between the tool’s documented behavior and its actual
capabilities.

2. Updated cron examples to use modern Codex defaults

Cron help text and examples now use gpt-5.4 as the primary Codex example,
instead of older gpt-5.2-codex guidance.

3. Updated cron rule files for agent guidance

The cron-related rule files now recommend current Codex model choices such as:

• gpt-5.4
• gpt-5.4-mini
• gpt-5.3-codex
• gpt-5.2

This ensures agents creating or editing cron jobs stop steering users toward
stale model recommendations.

4. Added tests

Added coverage for:

• editing provider/model/reasoning/CLI overrides in place
• clearing those overrides
• rejecting invalid --cli-parameters input

Why this is needed

Before this PR:

• cron runtime support for Codex gpt-5.4 already existed
• cron UX made that support look missing
• cron_edit.py could not actually perform several edits that its own docs and
  surrounding rules implied should be possible

After this PR:

• cron jobs can be updated to gpt-5.4 through supported tooling
• cron guidance matches runtime behavior
• users no longer need manual cron_jobs.json edits for normal model updates

Screenshot:

[viiccwen]

cc @PleasePrompto 🙌