Choosing a hidden library from the sidebar on a fresh launch opened the
topmost visible library instead, and reordering the sidebar changed which
wrong library appeared. A second attempt worked.
The first visit to the Libraries tab mounts LibrariesScreen, and two
post-frame callbacks then run in registration order: MainScreen's, which
applies the requested library, and the one initState registers during that
frame's build, which picks the saved or topmost-visible default. The second
one overwrote the first — and a hidden library can be neither default, so
the selection was always lost.
Initialization now treats an existing selection as authoritative, both on
entry and after each of its awaits, so a selection arriving while it is
suspended (the refresh() stale-resume path) also survives.
close#2207
edde746
582d419618