Every modal already mounts a .cx-backdrop element over its layer, so the
stacked variant painting another one as `0 0 0 100vmax` of shadow spread was
redundant, and the area beneath it was darkened twice.
It was also the most expensive declaration in the sheet: a spread the size of
the viewport diagonal, on an element inside a fixed layer, with an entry
animation running. Removed in favour of a bounded shadow, and a test reads the
stylesheet for the pattern -- asserting on node.style in jsdom passes against
any rule at all, since no CSS is applied there.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
