Function map_uris 

pub fn map_uris(uris: &[Url]) -> MultiOutcome

Map the portal’s returned URIs for a multi-select open: every local file:// path is collected, an empty list is a cancel, and a selection with no local file at all is a failure.

A mixed selection keeps the local entries and drops the rest — the user asked for those files, and refusing all of them because one was remote would be surprising.