Function run_with 

pub fn run_with(
    project: &Path,
    plan_path: &str,
    configure: &dyn Fn(&mut Command),
) -> Rendered

Like [run], but lets the caller layer extra configuration onto every spawned Command before it runs (an integration test’s PYTHONPATH, a hermetic KEEL_BACKEND, …) — mirrors crate::run::exec_with’s configure hook. run is exactly run_with(project, plan_path, &|_| {}).