[wieslawsoltes]

Problem

WebScene accepted and reflected clip-path: ellipse(...) but emitted no retained clip, so valid elliptical surfaces painted unclipped.

Change

• parse explicit pixel/percentage ellipse radii and an optional two-value center
• resolve geometry against the element border box
• emit a bounded SVG arc path through the existing indexed clip resource and balanced clip scope
• reject omitted/keyword radii and unsupported positions fail-closed
• add native retained-path and browser computed-value coverage

Validation

Tests and builds were deliberately not executed under the current implementation-throughput directive. Browser/native pixels, antialiasing, performance, memory, lifecycle, package, and CI gates remain required before release promotion and are recorded in #493/#256/#235.

Closes #493