[wieslawsoltes]

Problem

WebScene dropped qualified CSS rules nested inside style blocks. Unchanged VS Code OSS Settings therefore lost absolute positioning, shadow, grid, and split-view constraints.

Change

• Parse nested qualified rules, &, combinators, implicit descendants, selector lists, ordering, and media conditions.
• Preserve nested rule output through the native stylesheet sink and NativeWeb CSS service.
• Add parser, native layout, exact Chromium geometry, WPT-style, and bounded layout performance coverage.

Validation

• Rebased as one focused commit on current main (4235f2f6).
• CSS parser contract passes.
• Focused V8 native modal/grid/split geometry matches Chromium exactly.
• 500 positioned layouts complete in 6.079 ms against the 2,000 ms budget.
• NativeWeb CSS service passes.
• WPT reduction passes 1/1 documents and 4/4 subtests.
• git diff --check passes.

Integration

Closes #112.