RadioCards changelog

9ff88bf: fix(a11y): Command separators and RadioGroup arrow keys

• Command: Command.Separator is now hidden from assistive technology (aria-hidden, no role="separator"). A separator isn't an allowed child of the listbox it renders inside, so axe reported a critical aria-required-children violation.
• RadioGroup / RadioCards: all four arrow keys move between options, whatever the orientation, as the WAI-ARIA radio pattern specifies. Radix and Base UI do the same. orientation still sets aria-orientation.