Add keybindings for cycling TUI permission modes (#39873)

## What changed

- Add unbound `previous_permission_mode` and `next_permission_mode` actions to
  `tui.keymap.chat` so users can configure shortcuts that cycle through the
  available built-in permission modes.
- Apply shortcut selections only to the active session, without writing them
  to `config.toml`, and report update failures in the transcript.
- Exclude modes disallowed by managed requirements or platform safety checks,
  reject printable-key bindings, and ignore these bindings in project config.

## Testing

- Cover mode cycling, unavailable modes, session-only updates, server errors,
  stale threads, keymap validation, and project-config sanitization.

GitOrigin-RevId: c3cfdf1e732b7b7bfe8f53fcac19a37e593bbfab

codex-rs/tui/src/app/event_dispatch.rs

@@ -1519,6 +1519,9 @@ impl App {
                     profile_selection,
                 );
             }
+            AppEvent::ApplyPermissionShortcut { thread_id, selection } => {
+                self.apply_permission_shortcut(app_server, tui, thread_id, selection).await;
+            }
             AppEvent::OpenWorldWritableWarningConfirmation {
                 preset,
                 profile_selection,