Three changes to the view-cone runtime, none of which change what a cone
covers:

- A vertex where touching pieces of one stroke meet, with the boundary
  running straight through it, is no visibility event. Skipping it drops
  35-65% of a cone's polygon points and 20-45% of its time (native and Dart
  alike); cone areas match the old ones to 1e-8.
- A ray aimed at an exact corner could land 1e-11 past both adjoining
  edges and run on to the range (9 of 485,570 vertex rays in an all-map
  audit). Endpoint slack is now 1e-10 SVG units along the wall instead of
  1e-12 of the edge, far below the 1e-8 radian rays that must pass a corner.
- Cones that overlook Lotus's and Icebox's measured floors no longer build
  their lit area with ~1,000 sequential path subtractions (160-190 ms per
  cone). The floor pass now returns its shadows as shapes, and painters
  fill each floor and erase them in a layer. The boolean area is kept, built
  only when the sightline report asks for it.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>