Adds a paint feature to obscura-render (tiny-skia: pure Rust, CPU,
deterministic, no system deps). paint_dom lays out the DOM and fills
each element's border box with its parsed background-color over a white
page, in tree order so descendants paint over ancestors.
Style parsing now also extracts background-color (hex #rgb/#rgba/
later enhancements.
Parse inline style attributes into the layout-relevant subset of
LayoutStyle: display, width/height, margin, padding, and border width,
including box shorthands (1-4 values) and per-side longhands. !important
is stripped; auto and percentages leave the size unset for phase 1.
Layered on a small built-in UA default sheet. A compact hand-rolled
tokenizer handles inline attributes without a cssparser dependency; a
real cascade can harden it later.
SGavrl