chore(codex): add Codex CLI config and link mapping; update Brewfile

[HagaSpa]

Background / 背景

Introduce Codex CLI configuration and wiring so this repo can use the Codex agent locally alongside existing Claude Code settings. Add Homebrew dependency and link script mapping to make setup reproducible.
ローカルでCodexエージェントを利用できるように設定を追加しました。Homebrew 依存関係と link.sh でのシンボリックリンク設定を追加し、セットアップを再現可能にします。

Changes / 変更内容

• Add .codex/config.toml for local Codex CLI
• Update link.sh to link ~/.codex/config.toml
• Add brew "codex" to Brewfile
• Add AGENTS.md with repository conventions

.codex/config.toml を追加し、link.sh に ~/.codex/config.toml へのリンクを追記。Brewfile に codex を追加し、AGENTS.md を同梱しました。

Impact scope / 影響範囲

• Affects local developer environments during ./link.sh and brew bundle
• No runtime/CI behavior change expected
• New Homebrew package codex will be installed

ローカル開発環境のセットアップに影響します（./link.sh と brew bundle）。実行時/CI の挙動変更はありません。新規 Homebrew パッケージ codex が追加されます。

Testing / 動作確認

• bash -n link.sh passes

• brew bundle check --file=./Brewfile recognizes new formula

• bash -n link.sh が通ることを確認

• brew bundle check --file=./Brewfile で新規 formula が認識されることを確認

[claude]

Claude finished @HagaSpa's task —— View job

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Code Review Complete ✅

I've reviewed all the changed files in this PR. Here's my comprehensive feedback:

Review Tasks

• Read and analyze .codex/config.toml
• Review new AGENTS.md documentation
• Check Brewfile changes
• Review link.sh modifications
• Evaluate security implications
• Check integration with existing dotfiles structure
• Provide comprehensive feedback

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Overall Assessment: ✅ Approved with Minor Suggestions

This is a well-structured addition that follows the repository's conventions and integrates cleanly with the existing dotfiles architecture.

Code Quality & Best Practices

✅ Excellent

• Follows existing patterns: The PR correctly mirrors the Claude Code setup by adding .codex/ directory alongside .claude/
• Proper integration: Updates both Brewfile and link.sh consistently
• Documentation: Includes comprehensive AGENTS.md following the repo's style
• Atomic changes: Single, focused PR scope

✅ Configuration Structure (.codex/config.toml:1-7)

model_reasoning_effort = "high"
hide_agent_reasoning = true
network_access = true

[tools]
web_search = true

• Clean, minimal TOML configuration
• Sensible defaults for development workflow
• Follows standard configuration patterns

✅ Link Script Integration (link.sh:16)

".codex/config.toml:~/.codex/config.toml"

• Correctly placed in alphabetical order within the files_and_paths array
• Follows the established source:destination pattern
• Will work seamlessly with existing backup mechanism

Security Considerations

✅ No Security Concerns

• Configuration contains only behavioral settings, no sensitive data
• Network access is explicitly controlled through config
• No executable code or scripts in the config files
• Follows the repo's security guidelines from AGENTS.md:36-39

Performance Considerations

✅ Minimal Impact

• Single small config file addition
• No performance implications for the linking process
• Homebrew package addition is standard practice

Integration Analysis

✅ Perfect Integration

• Follows the modular approach described in CLAUDE.md
• Maintains consistency with existing .claude/ setup
• AGENTS.md correctly documents the repository structure and conventions
• Testing approach follows established patterns (bash -n link.sh)

Documentation Quality

✅ Comprehensive (AGENTS.md)

• Structure documentation: Clear module organization (lines 3-10)
• Development commands: Proper setup instructions (lines 12-17)
• Coding standards: Consistent with existing practices (lines 19-24)
• Testing guidelines: Follows established patterns (lines 26-29)

Test Coverage

✅ Adequate Testing

The PR description shows proper validation:

• bash -n link.sh passes - validates script syntax
• brew bundle check --file=./Brewfile recognizes new formula

Minor Suggestions for Future Consideration

1. Documentation Enhancement: Consider adding a brief section in README.md about Codex CLI alongside Claude Code documentation
2. Config Comments: The TOML config could benefit from inline comments explaining each setting's purpose
3. Version Pinning: Consider documenting compatible Codex CLI versions in AGENTS.md

Summary

This PR demonstrates excellent adherence to the repository's conventions and introduces Codex CLI support in a clean, maintainable way. The changes are minimal, focused, and follow established patterns perfectly. No blocking issues identified.

Recommendation: ✅ Merge when ready