scrollTo/scrollBy dispatch a scroll event; direct assignment did not. So the
usual lazy-load idiom
el.addEventListener('scroll', loadMore);
el.scrollTop = el.scrollHeight;
never reached the listener, and scroll-driven feeds stalled after their first
batch with no error to show for it.
Checked against a real Chrome over CDP, same probe on the same page:
Chrome el.scrollTop = 100 -> 1 scroll event
obscura (before) el.scrollTop = 100 -> 0 scroll events
obscura (after) el.scrollTop = 100 -> 1 scroll event
The setters only fire when the offset actually changes, so a loader that
rewrites the same scrollTop each frame does not re-enter. scrollTo/scrollBy
suppress the per-axis events and emit one for the whole movement, the way a
browser reports one scroll per operation rather than one per axis.
The offset stays unclamped on purpose. Without layout, any maximum is a guess,
and a guess derived from the synthetic scroll box pins scrollTop at 0, which
deadlocks the very loaders this unblocks: no scroll, no content, no scroll.
Geometry is left alone here — this is event dispatch only.
Tests: 4 of the 5 new cases fail without this change (the scrollTo coalescing
one passes either way; it guards against this change turning one event into
three). nextest -p obscura-cdp 91/91, obstacle course 33/33.