Have you considered how this will work for "binless" libraries (header-
only before modules, module interface-only after), which don't have the
"library file itself" (I assume you refer to the library binary, such
as .a/.so)?
Yes. When we discussed it we accepted that "interface unit only libraries" will depend on stronger package management convergence.
It's possible the pkg-config extension could just point to the metadata file in those cases.
But... There's some hint that "interface unit only" libraries may be less viable than people think.
Daniel