Function home_dir 

pub fn home_dir(mur_home: &Path, key: &str) -> PathBuf

<mur_home>/cli-homes/<key>/ — this backend’s private CLI home.

mur_home is a parameter rather than a call to trust::mur_home() so the path is a pure function of its inputs and every test runs against a temp dir. Same shape as local_llm::local_model_dir.