Zero-Shot Reranker Implementation

Implement a reranking stage for RAG retrieval results.

Retrieval Context:
{{retrieval_setup}}

Reranking Requirements:
{{reranking_specs}}

Latency Budget:
{{latency_constraints}}

Design and implement:
1. Reranker model selection and integration
2. Score normalization across sources
3. Batch processing for efficiency
4. Fallback when reranker unavailable
5. A/B testing framework for reranker comparison
6. Metrics collection for reranker performance