ConstElides in the MIDDLE rather than at the end: a path's two informative ends are the drive/host and
the file name, and a tail ellipsis eats the half that says which file this is. Done by splitting
at the last separator and letting only the head shrink, so it costs no measurement — the tail is
flex: 0 0 auto and the head carries the ellipsis.
Renders nothing when no source carries a directory. The title already says the file name, and repeating it as a path that is not one helps nobody (a book may record only a bare relative name — see externalBookLocation).
Where the linked file is — the card's bold label, under the icon and title.