The jump-to-unread FAB could surface an OutOfWindow target when the
fully-read marker event was either loaded-but-not-displayed (state/filtered
events) or when there was nothing displayable to jump to. Add two guards to
the recompute:
- Require roomInfo.numUnreadMessages > 0, so the FAB only appears when there
is genuinely unread "interesting" content (never state/hidden events).
- Add Timeline.isEventLoaded to distinguish "in the loaded window but not
rendered" from "genuinely outside the window", falling back to the SDK only
after the cheap display-index check (isKnown) misses.
The RustTimeline implementation reads the replay cache first and releases the
EventTimelineItem native handle via use {} when probing the SDK. Adds presenter
tests for the loaded-but-not-displayed and no-unread-messages branches.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Jenna Vassar
5a2977134b