Servo-replacement runtime for Tauri: wires html-cat, css-cat, dom-cat, layout-cat, paint-cat, net-cat, boa-cat, ecma-runtime-cat, and web-api-cat into a single rendering + scripting pipeline. v1.0.0 implements the `tauri_runtime::Runtime` trait surface (Runtime, RuntimeHandle, WindowDispatch, WebviewDispatch, EventLoopProxy, WindowBuilder) as a stub-heavy skeleton so it can be plugged into a Tauri app; non-cosmetic methods return `tauri_runtime::Error` and will be filled in over the 1.x patch series. The Servo no-AI policy disqualifies upstream contribution; this is the AI-built parallel.