"100%" in Preferences ▸ Interface size multiplied the scale the display
reports, so on a 1080p screen whose system reports 200 % it still drew at
200 % (#456). A chosen size is now absolute, as PhotoCraft's UI Scale is: the
display's scale is divided back out, so "100%" is one screen pixel per point.
Auto is unchanged (the display's scale times GNOME's text scaling), and its
menu entry now shows the size it draws at. The menu offers PhotoCraft's sizes,
75–300 %.
Co-authored-by: Brandon Thomas <echelon@gmail.com>