{#-
Light/dark switcher styled after the search button of the Zensical modern
variant: a square host (1.6rem, 0.4rem corner radius, faint fg--lightest
fill, hover fg--lighter) holding a single animated sun/moon glyph. The glyph
is a sun whose core scales up while a mask circle slides in to carve the
crescent and the beams fade out — the scheme change drives the whole morph
from CSS alone. The palette s and their