Function ensure_default_gguf_model 

pub fn ensure_default_gguf_model(home: &str) -> Option<PathBuf>

Ensure the canonical verification/benchmark GGUF model exists at ~/.mlstack/models/<FILENAME>, downloading it from the canonical URL if absent. Shared by the llama.cpp installer verification AND the benchmark runner so there is one download path and one model URL. Validates with is_gguf and removes any corrupt/error file left behind. curl -s keeps it silent so it does not corrupt the TUI’s alternate screen.