fix(tui): add missing Ctrl+n/Ctrl+p support to ListSelectionView (#7629)

## Summary

Extend Ctrl+n/Ctrl+p navigation support to selection popups (model
picker, approval mode, etc.)

This is a follow-up to #7530, which added Ctrl+n/Ctrl+p navigation to
the textarea.
The same keybindings were missing from `ListSelectionView`, causing
inconsistent behavior
  when navigating selection popups.

  ## Related

  - #7530 - feat(tui): map Ctrl-P/N to arrow navigation in textarea

  ## Changes

  - Added Ctrl+n as alternative to Down arrow in selection popups
  - Added Ctrl+p as alternative to Up arrow in selection popups
  - Added unit tests for the new keybindings

  ## Test Plan

  - [x] `cargo test -p codex-tui list_selection_view` - all tests pass
- [x] Manual testing: verified Ctrl+n/p navigation works in model
selection popup

---------

Co-authored-by: Eric Traut <etraut@openai.com>

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

@@ -268,13 +268,36 @@ impl ListSelectionView {
 impl BottomPaneView for ListSelectionView {
     fn handle_key_event(&mut self, key_event: KeyEvent) {
         match key_event {
+            // Some terminals (or configurations) send Control key chords as
+            // C0 control characters without reporting the CONTROL modifier.
+            // Handle fallbacks for Ctrl-P/N here so navigation works everywhere.
             KeyEvent {
                 code: KeyCode::Up, ..
-            } => self.move_up(),
+            }
+            | KeyEvent {
+                code: KeyCode::Char('p'),
+                modifiers: KeyModifiers::CONTROL,
+                ..
+            }
+            | KeyEvent {
+                code: KeyCode::Char('\u{0010}'),
+                modifiers: KeyModifiers::NONE,
+                ..
+            } /* ^P */ => self.move_up(),
             KeyEvent {
                 code: KeyCode::Down,
                 ..
-            } => self.move_down(),
+            }
+            | KeyEvent {
+                code: KeyCode::Char('n'),
+                modifiers: KeyModifiers::CONTROL,
+                ..
+            }
+            | KeyEvent {
+                code: KeyCode::Char('\u{000e}'),
+                modifiers: KeyModifiers::NONE,
+                ..
+            } /* ^N */ => self.move_down(),
             KeyEvent {
                 code: KeyCode::Backspace,
                 ..