Replace hardcoded tag-based defaults in the layout crate with CSS computed styles from the style crate. The layout engine now accepts a StyledNode tree instead of walking the DOM directly. Layout crate changes: - layout() takes &StyledNode + &Document instead of &Document alone - Remove hardcoded display_type(), default_font_size(), default_margin() - Read display, margin, padding, border, font-size from ComputedStyle - Carry color, background-color, text-decoration, border styles/colors on LayoutBox for the renderer to use Render crate changes: - Use CSS color for text (instead of hardcoded black) - Use CSS background-color for box backgrounds (skip transparent) - Render borders with correct width, style, and color - Support text-decoration: underline - Replace render-local Color type with we_css::values::Color Browser pipeline: - Full: HTML → DOM → extract CSS → resolve styles → layout → render 6 new tests across layout (3) and render (3) crates verifying CSS properties flow through to layout positions and paint commands. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>