Steerable Tauri host

Reusable native desktop host shipped inside the @steerable/agent-shell npm package. Consuming products keep a thin src-tauri crate that supplies Tauri configuration and calls steerable_agent_shell_tauri::run.

The host supervises the product's compiled Node BS entry on an ephemeral loopback port. Node continues to own storage, PTY, tools, approvals, packs, and CoreLoop sidecars. Rust owns the native window, menus, dialogs, single-instance behavior, screenshot clipboard transfer, process containment, resource paths, and updates.

The crate is source-distributed with the npm package and is not published to crates.io.

Packaged products place the complete portable Python sidecar at python-runtime/<platform> and the verified egress proxy at engine/steerable-egress-proxy. The Python runtime contains the native Rust CoreLoop engine. An optional engine/python-runner is only a child interpreter for run_code; it never hosts the sidecar. Products may set pythonRunner to sidecar, bundle, or download in product.json. Sidecar mode runs run_code with the packaged sidecar interpreter instead of a second CPython; the child stays confined by the run_code sandbox, but it can import the sidecar's installed packages. Download mode starts the product without an interpreter and lets the settings UI install one in the background. The default python-build-standalone archive is checked against the packaged SHA-256; users may instead choose an unverified custom archive URL or an existing Python 3.9+ executable. Download progress is emitted to the renderer, and the selected interpreter is passed as STEERABLE_PYTHON on the next application start.