Keeps the messages.js fix from @mysoul12138 (set _streamFinalized=true right
after the early-return guard, before the fade window, so a stream_end arriving
mid-fade can't call _restoreSettledSession and overwrite live messages with a
stale server snapshot). Drops the contributor's dead empty `else {}` block in
ui.js (no behavior). Adds a regression test pinning the immediate-finalize order.
Co-authored-by: mysoul12138 <mysoul12138@users.noreply.github.com>
