bg-elevated is fully opaque and only hue-matches --mf-bg (the plain
page background), so it stayed stark white on the hero/spotlight cards,
which use a separately-computed, more saturated gradient (--mf-hero-bg/
--mf-spotlight-bg). An opaque fill can never pick up that color no
matter what hue it's tied to.
Make it translucent (bg-elevated/45) with backdrop-blur-lg so it
samples and lightly tints whatever is actually behind it, hero card,
spotlight card, or plain background, instead of only matching one of
them.