Auto-skip git checks in `exec` by default and add `@` file reference support

What feature would you like to see?

Current Problem:

# Required now
codex exec --skip-git-repo-check "say hello"

# Want this  
codex exec "say hello"

Proposed Changes:

1. Auto-skip git checks in exec by default

• Add --require-git flag for users who need git validation
• Interactive mode unchanged
• (If strict backward compatibility is required) instead of changing exec defaults, introduce a new command (e.g., codex run or codex do) that behaves with auto-skip by default.

1. Add @ file reference support

``bash
codex exec "@file.js analyze this"
codex exec "@package.json @README.md explain project"
codex exec "@src/ find bugs"
``

Rationale:

• Most exec usage needs --skip-git-repo-check anyway
• File references eliminate copy-paste workflow
• Backward compatible with opt-in git checking
• Improves user experience for common workflows

Are you interested in implementing this feature?

Yes

Additional information