Track which react-horizontal-scrolling-menu items are on screen: useIsVisible(itemId | 'first' | 'last', defaultValue), useLeftArrowVisible/useRightArrowVisible, the options prop (ratio, rootMargin, threshold), items.getVisible()/subscribe/unsubscribe, and the async IntersectionObserver truth model (items must be seen once, menuVisible gating, non-reactive isFirstItemVisible reads). Load when disabling arrows at the edges, styling items by visibility, building progress indicators, or debugging flickering or dead arrows.
