feat: add /back option to shell command confirmation prompt

Hi,

Currently, when the model tries to run a shell command, it asks the user with choices like:

  Yes (y)
  Yes, always approve this exact command for this session (a)
  Edit or give feedback (e)
  No, and keep going (n)
  No, and stop for now (esc)

But if a user accidentally selects the wrong option—say they hit Edit or give feedback instead of Yes, always approve this exact command for this session—there’s no way to go back and choose again.

I’d like to suggest adding a /back command (or something similar) so users can return to the previous menu. What do you think?