Function move_event_file 

pub(crate) fn move_event_file(
    path: &Path,
    to: &Collection,
) -> Result<PathBuf, String>

An event’s file moved to another calendar (its editor, 21 October 2026), of any account, this device’s own to a server’s above all, so that an event filed there by mistake reaches your other devices: noted, written there, taken out here (vdir::move_item, a step cut short finished at the next look), never twice, never lost. The sync sends both: the new item there, the deletion here. Its new path.