Slash commands for `codex exec`

What feature would you like to see?

currently codex doesn't allow exec slash commands using codex exec (headless codex). from my pov - idea of slash cmd (which I proposed initially and also had PR) so that repetitive workflow / prompts can be abstracted without copy paste - this also apply for headless codex - e.g I want to run codex exec /review in gitlab/github/gerrit ci but currently I can't due to this limitation.

Are you interested in implementing this feature?

I can if needs to be but I think OAI team is well staff :P - let me know if you want to me to push PR.

Additional information

_No response_