Function merge_order 

pub fn merge_order(views: &[PrView]) -> Vec<u64>

2026-09-26: The recommended merge order over the orderable PRs, sorted by, in turn:

1. fewest conflict partners (the private contend helper);
2. fewest targets re-opened, with a whole-repo PR last;
3. fewest changed paths;
4. lowest PR number, which makes the order total.

super::PrFacts carries no check, review, mergeability or dependency state, so the order ignores them.