Function implement 

pub fn implement(
    instruction: &str,
    cwd: &str,
    language: &str,
    brief: Option<&str>,
) -> String

Prompt for an implementer.

brief is the design-deliberation stage’s synthesis (crate::advise::Advice::synthesis), when the stage ran and at least one advisor’s proposal was usable. None when [graph] advise is off, the stage found nothing usable, or the synthesis seat itself failed - the implementer then gets exactly the prompt it always did.