Function grounded_at_budget 

pub fn grounded_at_budget<A>(
    framework: &WeightedFramework<A>,
    budget: Budget,
) -> Result<HashSet<A>, Error>
where
    A: Clone + Eq + Hash + Debug + Ord,

Union of grounded extensions across all β-inconsistent residuals. Matches Dunne 2011’s credulous reading for the grounded semantics.