feat: Sandbox, Fork, and Apply commands

[joshrotenberg]

Summary

Codex-specific commands not in claude_wrapper.

Sandbox command (codex sandbox -- [args])

• SandboxPlatform: MacOs, Linux, Windows
• Runs a command inside the codex sandbox

Fork command (codex fork)

• Fork an existing session to try a different approach
• session_id, prompt, --last, --all, --model
• Similar args to Resume

Apply command (codex apply )

• Apply an agent diff as git apply

Acceptance criteria

• CodexWrapper.Commands.Sandbox with builder
• CodexWrapper.Commands.Fork with builder
• CodexWrapper.Commands.Apply
• Tests for arg building