Function resolve_venv_python 

pub fn resolve_venv_python(
    venv_name: &str,
    explicit: Option<&str>,
    package_dir: Option<&Path>,
) -> Option<String>

resolve_venv_python(venv_name, explicit) — the interpreter of an optional local-model venv (venv-whisper, venv-chatterbox, …).

An explicit path wins. With XIL_CODEROOT set, only $XIL_CODEROOT/<venv>/bin/python3 is considered. Otherwise the workspace root, then the repo root above the Python package (package_dir/../..), are tried.