Function withheld_family_lines 

pub(crate) fn withheld_family_lines(
    families: &BTreeSet<McpFamily>,
) -> Vec<&'static str>

The lines a worker’s prompt carries for the families it was NOT given: one per withheld family, in wire order. All families selected means no lines. This wording ships as the worker’s own instruction (rule 17), so it says what is absent and what to do instead.