- The canvas drop target sat above the moved pointer block, so a drag
  started as an editor could still land after the role dropped to
  viewer. The drop now checks edit access when it lands.
- Pressing a lineup end holds it, and a held lineup counted as editing
  in presence. Viewers now never broadcast lineup editing: the check
  lives in myLineupEditingProvider, so it covers holds, placements and
  open dialogs, and follows role changes while a panel is open. The
  panel's one-off check is gone.
- The tests now drive the real InteractiveMap, check the hovered delete
  target, and try to drag an ordinary placed agent; presence is checked
  in the provider test, where pages and lineup groups exist.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>