Display-list construction: walks a layout-cat LayoutTree and emits a sequence of PaintCommands (FillRect, StrokeRect, FillText) for a backend renderer to consume. v0.2.0 adds `PaintCommand::scaled(factor)` and `DisplayList::scaled(factor)` that return a new command / list with rect geometry, stroke width, and font_size all multiplied by `factor` -- useful for zoom-style backends that want to re-rasterize text at the larger glyph size rather than bitmap-scaling the output. Backend-agnostic; no platform graphics dependencies. No mut, no Rc/Arc, no interior mutability, no panics, exhaustive matches. Fifth sub-crate of a Servo-replacement webview runtime targeting Tauri.