Add Codex plugin support alongside Claude Code

[lx-0]

Make ytstack installable as a Codex plugin. Both hosts load the same 21 existing skills directly from skills/ and reuse the lifecycle scripts in hooks/. All skill files, their resources, the Claude manifests, and vendor content are unchanged against main.

• Add Codex plugin metadata and a repository self-marketplace.
• Register SessionStart, PreCompact, and SessionEnd through a small compatibility helper. It supplies the shared scripts' existing path variables and resolves the repository root when a session starts in a subdirectory.
• Supply one central Codex runtime guide at SessionStart. Without trusted hooks, read that guide explicitly before loading a skill. Claude startup receives no Codex instructions.
• Keep Claude Agent Teams and edit/commit hooks outside Codex support. Document setup and the sequential workflow.

There is one skill tree and one set of hook implementations. No generator, copied skills, copied resources, or copied hook scripts.

Validation:

• 13 integration tests pass: both hosts' six verbatim vendor imports, startup isolation, packaging, paths with spaces, root/subdirectory lifecycle behavior, handoff, journal entries, and relative skill writes.
• Fresh Codex CLI 0.162.1 profile: installation succeeds; app-server discovery loads all 21 original skill files and exactly three hooks with no errors or warnings. Hooks remain untrusted until user review.
• Existing Claude commit-hook regression is included in CI. bin/ytstack-check reports no failures and the same 109 baseline warnings. git diff --check passes.

The interactive desktop walkthrough after hook trust remains a manual follow-up in REVIEW-NOTES. No user-profile installation or release is included.

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[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-13T09:06:01.764632Z	748376d	PR opened

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review" or "@codex security review".

Codex reacts with 👀 while any review is running, comments if it has suggestions, and reacts with 👍 once all reviews finish with no findings.

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 748376d294

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

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