The sidecar is a private local process owned by the Electron main process. It communicates over newline-delimited JSON-RPC on stdin/stdout and owns the desktop SQLite data directory.

Build locally with:

cargo build --manifest-path crates/desktop-sidecar/Cargo.toml

The first milestone exposes system.info, storage.health, and app.shutdown. Domain storage and sync methods will be added behind the same protocol without exposing Node.js APIs to the renderer.