Repository keeps one live Timeline per room and re-yields on its
onUpdate callback (fires for both live events AND requestHistory),
not just onSync which never fires for pagination. loadMoreMessages
now paginates that same instance; added canLoadMore.
Timeline widget requests older history when scrolled within 400px of
the oldest end, guarded against re-entry, with a top loading spinner.
Verified: widget test drives a drag-to-top and asserts loadMoreMessages
fires; live smoke test confirms the onUpdate delivery path (reused by
history) still shows new messages after the refactor.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
B6 scroll-to-latest: ScrollController on the timeline; a small
arrow-down FAB fades in once scrolled >400px up and animates back
to the newest message on tap (overlaid on the list, not the FAB slot)
B5 panic hold-ring: 700ms AnimationController drives a red progress
ring around the panic icon; haptic + fire on completion, silent
reset on early release; tap-hint and configured guard preserved
Panic ring verified in-browser (ring fills, alert fires to the room).
Scroll-to-latest verified with a deterministic widget test because the
CanvasKit surface rejects synthetic scroll input in headless Chromium.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
