Introduces yaak-rpc (shared RPC infrastructure) and yaak-proxy-lib
(proxy app logic decoupled from any frontend). A single Tauri command
dispatches all RPC calls through a typed router, with TypeScript types
auto-generated via ts-rs and a generic rpc() function for type-safe
calls from the frontend.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>