Hybrid Search Implementation

Implement a hybrid search system combining dense and sparse retrieval.

## Requirements
{{search_requirements}}

## Data Characteristics
{{data_characteristics}}

## Technology Stack
- Vector store: {{vector_store}}
- Full-text search: {{fts_engine}}

Create a complete implementation:

```python
class HybridSearcher:
    def __init__(self, dense_weight: float = 0.7):
        # Initialize both retrievers
        pass
    
    def search(self, query: str, top_k: int) -> List[Result]:
        # 1. Dense retrieval
        # 2. Sparse retrieval  
        # 3. Score fusion (RRF)
        # 4. Reranking
        pass
```

Include:
- Reciprocal Rank Fusion implementation
- Weight tuning methodology
- Evaluation metrics
- A/B test setup