The cost usage submenu set `menu.delegate = self` (the MenuSessionsInjector),
which caused `menuWillOpen(_:)` to call `inject(into:)` on the submenu when
it opened. This re-inserted the "Usage cost (30 days)" item into the submenu,
creating an infinite recursive dropdown.
Fix: remove the delegate assignment from the submenu — it does not need
the injector's delegate behavior since it only contains a static chart view.
Closes#25167
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>