Query Rewriting Pipeline

Implement a query rewriting pipeline to improve RAG retrieval.

## Current Query Examples
{{query_examples}}

## Retrieval Challenges
{{retrieval_challenges}}

## Available Context
{{available_context}}

Build a multi-stage rewriting pipeline:

```python
class QueryRewriter:
    def rewrite(self, query: str, context: dict) -> List[str]:
        """
        Stage 1: Query expansion (synonyms, related terms)
        Stage 2: Query decomposition (complex -> simple)
        Stage 3: Hypothetical document generation (HyDE)
        Stage 4: Query variants for ensemble retrieval
        """
        pass
```

Include:
- LLM-based vs rule-based rewriting
- Caching rewritten queries
- Evaluation metrics for rewriting quality
- A/B testing framework