Add Codex adapter support

[JaeCoding]

Summary

• Add repo-scoped Codex support with AGENTS.md, .codex/config.toml, and generated .agents/skills/* wrappers that point back to upstream .claude/skills as the source of truth.
• Add tools/sync_codex_skills.py and run it from setup so Codex wrappers stay in sync after language switches or upstream skill updates.
• Preserve the existing Claude Code /skill ... intent flow and add a separate codex_prompt plus Codex adapter doc path for Codex users.
• Document a Codex quick-start flow in README while keeping Claude Code as the existing primary path.
• Install httpx with the main requirements so the review MCP server can start from Codex config.

Checklist

• python -m pytest tests/ -v passes — not run: this repo currently has no tests/ directory, and local pytest exits with no tests ran.
• Both i18n/en/ and i18n/zh/ updated (if modifying skills/CLAUDE.md/shared-references) — not applicable; upstream skill/i18n source files were not changed.
• ./setup.sh run to sync active files (if i18n files changed) — not applicable; ran Codex wrapper sync directly instead.
• docs/extending.md checklist followed (if adding new module) — not applicable; no new runtime module added.
• No src/ packages created (this is a Claude Code skill project).

Verification

• python3 tools/sync_codex_skills.py --check
• python3 -m py_compile tools/sync_codex_skills.py tools/serve.py mcp-servers/llm-review/server.py
• bash -n setup.sh
• Started python3 tools/serve.py --host 127.0.0.1 --port 9877 and verified POST /api/intent/discover keeps command as /discover ... while adding codex_prompt.
• git diff --check before amend.