zeta: Adjust reviewing UI (#21932)

Most notably, adding a title bar-ish in the left column as so to add the
"from most recent to oldest" info, which is supposed to make scanning
the list of completions easier to do (at least it would've helped me
figure out that was sorted that way when I was wondering about it!).

<img width="800" alt="Screenshot 2024-12-12 at 16 24 36"
src="https://github.com/user-attachments/assets/1acc9951-3df0-4cd2-96ff-94ed555ecae5"
/>

Release Notes:

- N/A