Function propose_each 

pub fn propose_each<F>(input: &[u8], limits: Limits, emit: F) -> Result<()>
where
    F: FnMut(Candidate) -> Result<()>,

Generate the candidate set one candidate at a time, invoking emit for each. Same set, same order as propose_all, but the streaming form lets the court keep only one unpriced candidate’s payload resident, which bounds encoder memory on large inputs (Phase 14).