Menubar / navigation-menu pattern with single-level submenus. Top-level items
use a roving tabindex with orientation-aware arrow navigation; submenu
triggers expose aria-haspopup/aria-expanded and open on Enter/Space/arrow
or click. Submenu items support arrow/Home/End/typeahead, Escape to close,
and Left/Right to move between adjacent top-level menus.
Menubar / navigation-menu pattern with single-level submenus. Top-level items use a roving tabindex with orientation-aware arrow navigation; submenu triggers expose
aria-haspopup/aria-expandedand open on Enter/Space/arrow or click. Submenu items support arrow/Home/End/typeahead, Escape to close, and Left/Right to move between adjacent top-level menus.