const FOV_MIN: 20
The angles a lens on this build may be set to, degrees.
20° is a telephoto; past 110° everything fisheyes. Stated as angles even though the lens is canonically a focal length, because the limits are perceptual claims about a picture and a focal length is only a claim about a picture once you know the gauge.
Here rather than beside the slider that spends them, because two things
outside the shell solve against the same range: riseStance's lens, which
clamps at the long end and says so, and the terrain predicate, whose
saturation at 20° is the reason the long end is where it is
(docs/adr/0017-the-lens.md).