Not TUI based but I made something called meatcheck. The idea being that the LLM requests a review from the human, you can leave inline comments like a PR review.

Once you submit it outputs to stdout and the agent reads your comments and actions them.

https://github.com/jfyne/meatcheck

Thank you! At a glance this is very close to what I had in mind, especially with the straightforward output format, I'll give this a try.