- A viewer's flush queues nothing, so it no longer counts as proof when
  an editor's flush before the demotion couldn't queue the canvas. The
  page session remembers that, and forgets it when a page replaces the
  canvas. (Comparing the canvas to its server base doesn't work for a
  viewer: loading normalises old pages, so they never match.)
- Export Library and folder export check the account again once the
  backup is written; sendCloudWork checks it again before succeeding.
- The signed-out share-link video test is signed out again, and a canvas
  queued on a later try now has a success test.

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