RAG with Citations

Offline retrieval that cites sources like an adult, not like a model vibes-printing footnotes.

# c-02-rag-citations

Return an answer plus at least one citation dict with `id` and `snippet` for an offline corpus. Reranking must be deterministic — no random tie breaks.

## Validator

From repo root:

```bash
npm run challenge -- rag-citations --track langchain
```

Or from this package directory:

```bash
cd challenges/langchain/c-02-rag-citations
uv run python tests/validate.py
```

Hints

• Token overlap is primitive; deterministic rerank rules are how you avoid flaky tests.
• The validator looks for `doc-widget` and actual substring overlap in `snippet`.
• If two docs tie, break ties with a stable secondary key — priority, then id.

Acceptance

• `npm run challenge -- rag-citations --track langchain` exits 0
• `answer_query` returns `answer` plus `citations` with `id` and `snippet`
• Widget queries surface `doc-widget`; Runnable jargon surfaces `doc-lc`