Remove Codex workflow hooks, plan handling, and validation scripts

[SoraSuegami]

Summary

• Remove Codex workflow plumbing for session start, stop, and planning hooks.
• Remove shared Python helpers for workflow paths, runners, atomic writes, transcript handling, and CLI entry points.
• Remove JSON schemas and repo validation coverage for review decisions and session start intent.
• Update repository guidance docs to remove the new workflow and expected agent behavior.
• Remove shell wrappers for build checks, test execution, and hook invocation.

Testing

• Not run (not requested)

[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: d1526248c6

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[chatgpt-codex-connector]

Restore the hook manifest

With this manifest removed and codex_hooks also disabled in .codex/config.toml, Codex no longer registers the SessionStart and Stop commands for this repo. In Codex sessions that rely on the repository workflow, plan initialization, stop-time validation gates, and final read-only review are all bypassed instead of being enforced.

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