distribution.md §4, outstanding.md's FR-PLAT-LIN-3 entry, the Flatpak
manifest's comment and the README all said a library was chosen by
typing a path and that nothing in the tree called the FileChooser
portal. Since 6683c14 every folder the desktop asks for is chosen
through rfd's xdg-portal backend, so those sentences were false.
What they now say instead is narrower than "it works in the sandbox":
no Flatpak has been built here, so whether the portal's path opens a
library, holds across a restart and takes a sidecar is unobserved, and
volumes() still cannot see a host card. The chooser also landed in ui/
rather than behind the dr-plat seam distribution.md had proposed, and
both documents say so. FR-PLAT-LIN-3 gets a status note to the same
effect.