One hub control that fans its sibling toggles out on hover — a column, a
row split around the hub, or an arc — with the discs portalled past any
overflow-hidden parent and re-anchored on scroll and resize. Hover state,
geometry and open/close timing live in the primitive so a consumer only
re-renders when its own items change.
A document-level pointer watchdog closes the fan when enter/leave is
skipped: a disc that goes disabled under the pointer (a toggle turning
pending right after its click) stops receiving pointer events, so its
pointerleave never fires and the fan stayed open.
Discs wear the new Button `floating` variant off (popover fill +
shadow-md, glyph-only hover) and `default` on, so a toggled state is an
opaque primary disc rather than a translucent tint.
brooklyn!
c7580f0e06