update for 1. 优化 2.中英切换

backend/app/infrastructure/vectorstore/pass_through_reranker.py

@@ -0,0 +1,21 @@
+"""No-op reranker stub.
+
+Returns the original candidate list sliced to top_k.
+Replace with CrossEncoderReranker when a local cross-encoder model is available.
+"""
+from __future__ import annotations
+
+from app.domain.retrieval.models import RetrievedChunk
+from app.domain.retrieval.ports import Reranker
+
+
+class PassThroughReranker(Reranker):
+    """Pass-through reranker that preserves original retrieval order.
+
+    Acts as a placeholder for future cross-encoder reranking (e.g. ms-marco-MiniLM).
+    Wire via bootstrap.get_compliance_reranker() when ready to swap.
+    """
+
+    def rerank(self, query: str, chunks: list[RetrievedChunk], top_k: int) -> list[RetrievedChunk]:
+        """Return the first top_k chunks without reordering."""
+        return chunks[:top_k]