docs: comprehensive Codex feature analysis from git clone (#177)

- Cloned OpenAI Codex repository and analyzed source code directly
- Updated RECOMMANDATIONS.MD with technical documentation of Codex features
- Added detailed implementation guides for missing features:
  - Network Proxy with SSRF protection and domain pattern matching
  - Multi-Agent Collaboration system (spawn_agent, send_input, wait, close_agent)
  - Shell Snapshot system for performance optimization
  - ThreadManager for session management
  - TUI Backtracking system for conversation undo
  - Feature Flags with stages (Experimental, Stable, Deprecated)
  - Collaboration Modes (Plan, Code, PairProgramming, Execute)
  - Starlark Execution Policy engine
  - Agent Control System with guards and limits
- Includes code examples from Codex source files
- Added prioritized implementation roadmap

Co-authored-by: Droid Agent <droid@factory.ai>

Author: echobt