Accessibility
Fieldset, FieldsetLegendVisibility, FieldsetType from @prepared911/ui/fieldset.
The legend provides the accessible name for the group. Hidden legends remain in the tree through VisuallyHidden inside legend.
Group-level description and error ids are referenced from aria-describedby on the fieldset, not duplicated on each child control.
FieldsetType.RadioGroup exposes role="radiogroup" while the legend still names the collection.
Error announcement. An error that appears or changes after the control mounts is announced politely once, unless it comes from a submit attempt that the enclosing Form speaks for with its focus move or summary. A cleared error announces nothing. A Form opts out with announceFieldErrors={false}.