Function canonical_gguf_path 

pub fn canonical_gguf_path(model_dir: &Path, repo_id: &str) -> PathBuf

Where the canonical, always-F32 GGUF for repo_id lives once converted once. Every per-model convert command checks this path first: if present, it recasts straight from this cached GGUF to whatever dtype was requested instead of re-downloading and re-converting from HuggingFace.