Support two-stroke TUI key chords (#36511)

## What changed

- Accept two-stroke bindings such as `ctrl-x ctrl-s` in TUI keymap configuration while preserving arrays as alternative bindings.
- Route chords through the active TUI context, show pending and configured chord hints, and cancel pending chords on `esc`, context changes, or a one-second timeout.
- Extend `/keymap` to capture, add, replace, and display key chords.
- Reject chords that conflict with active single-key bindings, overlapping-context chords, or reserved terminal shortcuts.

## Testing

- Add coverage for chord parsing, validation, matching, timeout and cancellation behavior, context dispatch, key capture, and rendered shortcut hints.

GitOrigin-RevId: dfdede03f518d4936ad8621ebf5537026f2b282e

codex-rs/tui/src/chatwidget/constructor.rs

@@ -82,7 +82,7 @@ impl ChatWidget {
             .map(|keymap| keymap.chat.clone())
             .unwrap_or_else(|| default_keymap.chat.clone());
         let queued_message_edit_hint_binding = queued_message_edit_hint_binding(
-            &chat_keymap.edit_queued_message,
+            runtime_keymap.as_ref().unwrap_or(&default_keymap),
             current_terminal_info,
         );
         let pet_http_client = codex_http_client::RouteAwareClientPool::new(