Two cooperating bugs let the pagination skeleton stick at the top of the
chat across channel switches: (1) the browser's post-clamp scroll event
on channel switch fired the load-more block on the new channel, and
(2) useDelayedLoading's threshold timer refreshed displayStart on every
fire, extending the minDisplay window unboundedly when isLoading cycled.
- useDelayedLoading: stamp displayStart only on the false→true show
transition (functional setShow form to avoid stale closures).
- MessageList: suppressNextLoadMoreRef armed in Effect 3, consumed by
the load-more block on the next scroll event, with a 250 ms fallback
disarm so legitimate user scrolls aren't silently dropped. Suppression
scoped to the load-more block only.
- Regression test for the displayStart refresh bug.
- Updated docs/systems/message-list.md history.
Jannis Braun
d793ab8f78