Function fold_project_in 

fn fold_project_in(
    slug: &str,
    projects_prefix: &str,
    projects_root: &Path,
) -> (String, bool)

Testable core of fold_project. projects_prefix is the encoded <home>/Projects/ string to strip; an empty prefix disables the repo-resolution rule (no known home). projects_root is the real directory the candidate repo names are stat’d against.