Tracks the post-clamp scrollTop of every programmatic scroll-to-bottom in
lastProgrammaticBottomScrollRef. handleScroll skips the at-bottom flip and
re-pins when the event's scrollTop matches the sentinel — i.e., the event
was queued by our own command and layout grew underneath. User scrolls
break the match (scrollTop changes) and flow through the normal path.
This complements the 2026-03-25 race-fix (which gated auxiliary effects on
isAtBottomRef) by also preventing handleScroll from flipping that ref to
false based on a post-growth distance measurement of our own scroll.
Jannis Braun
d18845acb5