An app bar's overflow menu is two separate <x-menu> instances trading
places as the width crosses 600px, each display: none where the other
shows. Resizing away from a menu's trigger left its popover in an open
state forever, anchored to a wrapper nobody could see or reach anymore.
A ResizeObserver on the trigger now closes the menu once it has no box
left to render (plan step 36, navigation group).
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Qwx5USif3wFFmxtHg5U1g9