A knockout element with one opaque Normal solid fill (a path or
compound, no mask, effects or isolation) is drawn once under
AntiAlias::None, including the internal hard-edge frame of Art
Optimized supersampled exports, instead of being erased and added back
through per-element backdrop layers. Analytical antialiasing keeps the
existing compositor and rounding.
Exact-pixel tests compare against the general knockout path for paths
and compound holes across precision, supersampling, translucent parents
and copied backdrops, and check that the backdrop rasters are skipped;
translucent fills keep their knockout compositing.
# Conflicts:
# docs/roadmap.md
# docs/target-app-parity.md