ep: Compute kept rate even when there's no matches (#55912)

Previously, we were skipping examples with zero overlap, inflating the
aggregated metric


Release Notes:

- N/A

Co-authored-by: Ben Kunkle <ben@zed.dev>
c83f3fe581Oleksiy Syvokon committed on 5/6/2026, 4:11:45 PM· committed by GitHubparente0b43b3
1 file changedLine totals unavailable