Replace the RAF easing follow loop + settle burst with an always-on
instant-follow model: while pinned, the content ResizeObserver re-pins to
the bottom synchronously (scrollTop = scrollHeight, before paint) and is
the only writer of scrollTop. A position+TTL auto marker distinguishes our
own programmatic writes from genuine user scrolling, so a scroll event that
lands at the just-written bottom never trips a false release.
This removes the feedback loop where the easing animation, growing content,
and the user's own scroll all fought for scrollTop in the same frame -- the
infinite twitch when scrolling down during streaming, and the jiggle on
send / from the queue. The public hook interface is unchanged; all
consumers keep working untouched.
Bohdan Triapitsyn
757c704956