tauri-runtime-servocat 3.19.0

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. v3.19.0 persists `WebviewState.local_storage` to disk: a per-webview file under `$HOME/.tauri-runtime-servocat-storage/<label>/local.bin` loads on construct and saves after every successful eval, so localStorage values survive webview close + reopen. `sessionStorage` stays in-memory per the Storage spec (each webview instance is its own session). Seventh sub-crate of a Servo-replacement webview runtime targeting Tauri.