Brutalist Dropdown Menu

Dropdown Menu inherits Base trigger/content/item semantics and applies rounded flat panels and elevated Button-like triggers.

Group and Label provide a live accessible naming relationship; Separator and Shortcut are real passive parts. Shortcut only displays a hint and does not register a global binding. Decorative parts do not enter the action collection or add a press owner. The demo uses a 160px menu, grouped account/resources actions and a disabled API action. The real Invite users submenu is a separately pending protocol slice, not a simulated demo box. Checkbox/radio variants and complete native/GPUI, compiler, packed, visual and independent acceptance remain open.