fix(audit): correctness wave — ghost sends, Escape coordination, panel exclusion

- ScheduledMessagesTray: cancel prunes local state ONLY on confirmed server
  cancel; failures keep the item + show an inline error (was: a failed cancel
  looked cancelled but still sent at the scheduled time).
- Escape semantics: the composer consumes Escape (preventDefault+stopPropagation)
  iff autocomplete is open or a reply draft is set; the thread panel and Room's
  markAsRead act only on unconsumed Escape, and markAsRead defers entirely while
  a thread panel is open (listener order made it fire before the panel closed).
- Room: thread panel / media gallery are mutually exclusive (most-recently-
  opened wins); on mobile at most one right panel renders (thread > gallery >
  members) instead of stacked fullscreen overlays.
- RemindMeDialog: busy-disabled presets (no more double-click duplicates),
  try/catch with inline error, close only on success.
- ThreadTimeline: "Jump to Latest" floating chip when scrolled up (RoomTimeline
  idiom).

From the 4-auditor deep-audit wave; reviewer-verified.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/features/room/thread/ThreadPanel.tsx

@@ -123,6 +123,10 @@ export function ThreadPanel({ room, threadId, requestClose }: ThreadPanelProps)
     useCallback(
       (evt) => {
         if (isKeyHotkey('escape', evt)) {
+          // The composer preventDefaults Escape when it consumes it (dismissing
+          // autocomplete / clearing a reply draft). Don't close the panel in
+          // that case — only when Escape wasn't already handled.
+          if (evt.defaultPrevented) return;
           evt.preventDefault();
           evt.stopPropagation();
           requestClose();