The scroll listener on .cookbook-body never fired — the user is
likely scrolling inside the nested .hwfit-list (max-height:52vh)
which doesn't bubble to its parent. IntersectionObserver fires
whenever the Direct Download header crosses the viewport edge
regardless of which container moved.
Folds only when boundingClientRect.top < 0 (header pushed up past
the top) so modal close / detach doesn't trigger it.
74e563dabc