feat: Comprehensive hooks system for tool, file, and event lifecycle

[am-will]

Summary

• Implements a comprehensive hooks system allowing external commands to be triggered at various lifecycle events
• Adds support for tool hooks (before/after tool execution), file hooks (before/after file writes), and event hooks
• Includes prompt gating, stop hooks, compact mode, and notification hooks
• Global hooks ordering for predictable execution
• Full test coverage for hook events and tool hooks

Test plan

• Unit tests for hook_events
• Unit tests for tool_hooks
• Build validation passes
• Manual testing of hooks in various scenarios

[github-actions]

All contributors have signed the CLA ✍️ ✅
_{Posted by the CLA Assistant Lite bot.}

[am-will]

I have read the CLA Document and I hereby sign the CLA

[etraut-openai]

Our contribution guidelines state that we're not accepting feature contributions at this time. We need to make sure that all new features are well designed, compose well with both existing and upcoming features, fit into our roadmap, and are consistent across all Codex surfaces (CLI, IDE extension, web). If you would like to propose a new feature, please file or upvote an enhancement request in the issue tracker. We will generally prioritize new features based on community feedback.

[am-will]

Sorry boss, I didn't read it 😆 Codex was the one that replied to you. Thanks though. Love the new features you've dropped 🙌

Our contribution guidelines state that we're not accepting feature contributions at this time. We need to make sure that all new features are well designed, compose well with both existing and upcoming features, fit into our roadmap, and are consistent across all Codex surfaces (CLI, IDE extension, web). If you would like to propose a new feature, please file or upvote an enhancement request in the issue tracker. We will generally prioritize new features based on community feedback.