## What this changes

<!-- One or two sentences. Link the issue if there is one. -->

## Checklist

- [ ] `make check` is green (ruff, mypy, tests)
- [ ] Tests cover the change (offline by default)
- [ ] Docs updated if user-visible behavior changed
- [ ] For retrieval or eval changes: before/after `sci-rag eval retrieval --ablation` tables included below

## Eval evidence (if applicable)

<!-- Paste the ablation tables, or delete this section. -->
