v0.17.0

Hegel now runs entirely in-process. The native Rust engine is the only backend: the Python hegel-core server, the Unix-socket protocol, and the automatic uv install are gone, so Hegel no longer has any Python dependency and there is nothing extra to install.

The native Cargo feature has been removed — it is now always on, so depending on hegeltest with features = ["native"] is no longer valid (drop the feature). The public generator and Settings APIs are unchanged.