Function is_registered 

pub fn is_registered() -> bool

Whether everything sync_app_directory writes is already on disk.

The setup pass needs a “is this missing?” question it can answer without doing any work, because it runs on every install, upgrade and devp init. Rewriting a few hundred kilobytes of PNG each time would be harmless but wasteful, and on Linux it would also re-run update-mime-database, which is not free.

Content is not compared, only presence — the assets are compiled into the binary, so the upgrade stamp already forces a rewrite when the version changes.