Six reported defects, one root theme — our port diverged from the
reference semantics:
- a user gesture no longer collapses the reserved anchored end space
(that snap-to-bottom was the 'anchoring vanishes on a micro-scroll');
it only disarms the follow/anchor machinery, and anchor remeasures
after the user takes over can no longer re-position the viewport
- the anchor arms synchronously BEFORE the send reaches the store, and
the claim compares against the arm-time baseline — arming a frame
after the optimistic row committed is why anchoring 'rarely worked'
and sending from mid-history did nothing
- gestures are selective (wheel up, touch/pointer away from the end,
PageUp/Home/ArrowUp), so scrolling toward the end or clicking a row
at the live edge no longer kills follow
- 'at end' is a tight 40px band against the full content length instead
of the list's half-viewport isNearEnd, so the scroll-to-bottom pill
appears when the viewport actually leaves the end
- reaching the end re-arms follow without knocking an anchored turn out
of its mode, and the overlay scrollbar suppression follows scroll
ownership rather than the anchor's mere existence
- the status/working row moved out of the list footer to a fixed spot
above the composer: inside the list it walked down with every
streamed line, and its unmount was part of the end-of-stream jerk