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/bottom_pane_view.rs

@@ -28,6 +28,17 @@ pub(crate) trait BottomPaneView {
     /// Render the view: this will be displayed in place of the composer.
     fn render(&self, area: Rect, buf: &mut Buffer);
 
+    /// Optional paste handler. Return true if the view modified its state and
+    /// needs a redraw.
+    fn handle_paste(&mut self, _pane: &mut BottomPane, _pasted: String) -> bool {
+        false
+    }
+
+    /// Cursor position when this view is active.
+    fn cursor_pos(&self, _area: Rect) -> Option<(u16, u16)> {
+        None
+    }
+
     /// Try to handle approval request; return the original value if not
     /// consumed.
     fn try_consume_approval_request(