Function detect_duress 

pub fn detect_duress(
    imbalance: f32,
    explicit_threat: bool,
    threshold: f32,
) -> bool

Map a relational power-imbalance signal to a duress finding. imbalance is a normalised [0,1] measure of relational asymmetry (dependency / authority / economic capture); an explicit_threat forces duress regardless. At/above threshold, or under an explicit threat, the act is coerced → the resulting stipulation is voidable (never auto-void; the election stays with the victim — see module header).