Setting a map, theme, lineup or item back to what the server has, while
an earlier change to it was still on its way, queued nothing: the queue
ignores "nothing to write" while a change is being sent, so that change
landed and undid the user's. Now the canvas's values are written behind
it instead, and only dropped when nothing waiting can still land.

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