The unload endpoint checked is_loaded (requires healthy=True), but
during initial loading the server is not yet healthy. Cancel had no
effect because the unload route fell through to the Unsloth backend.
Fix: add is_active property (process exists, loading or loaded) and
check it in the unload route so cancel kills llama-server even during
the download/loading phase.
Also: toast cancel button now properly triggers the backend unload.
226ece0c9e