// Shared hooks — loaded before all other components
function useIsMobile(breakpoint = 768) {
  const [isMobile, setIsMobile] = React.useState(() =>
    typeof window !== 'undefined' && window.innerWidth <= breakpoint
  );
  React.useEffect(() => {
    const mq = window.matchMedia(`(max-width: ${breakpoint}px)`);
    const onChange = (e) => setIsMobile(e.matches);
    mq.addEventListener('change', onChange);
    setIsMobile(mq.matches);
    return () => mq.removeEventListener('change', onChange);
  }, [breakpoint]);
  return isMobile;
}

Object.assign(window, { useIsMobile });