feat: Add more /review options (#3961)

Adds the following options:

1. Review current changes
2. Review a specific commit
3. Review against a base branch (PR style)
4. Custom instructions

<img width="487" height="330" alt="Screenshot 2025-09-20 at 2 11 36 PM"
src="https://github.com/user-attachments/assets/edb0aaa5-5747-47fa-881f-cc4c4f7fe8bc"
/>

---

\+ Adds the following UI helpers:

1. Makes list selection searchable
2. Adds navigation to the bottom pane, so you could add a stack of
popups
3. Basic custom prompt view

codex-rs/tui/src/bottom_pane/popup_consts.rs

@@ -3,3 +3,6 @@
 /// Maximum number of rows any popup should attempt to display.
 /// Keep this consistent across all popups for a uniform feel.
 pub(crate) const MAX_POPUP_ROWS: usize = 8;
+
+/// Standard footer hint text used by popups.
+pub(crate) const STANDARD_POPUP_HINT_LINE: &str = "Press Enter to confirm or Esc to go back";