Function compute_ranked_diff 

pub fn compute_ranked_diff<E: DiffableRankEntry>(
    current: &mut [E],
    baseline: &[E],
)

Compute per-entry deltas between current and baseline entries.

For each entry in current, finds the matching baseline entry by DiffableRankEntry::diff_key and computes current_score - baseline_score. New entries (no baseline match) get delta = current_score. After this, current is sorted by |delta| descending.