fix(reranker): respect config.top_k in Cohere and ZeroEntropy fallback paths (#5560)

mem0/reranker/cohere_reranker.py

@@ -82,4 +82,5 @@ class CohereReranker(BaseReranker):
             # Fallback to original order if reranking fails
             for doc in documents:
                 doc['rerank_score'] = 0.0
-            return documents[:top_k] if top_k else documents
+            final_top_k = top_k or self.config.top_k
+            return documents[:final_top_k] if final_top_k else documents

mem0/reranker/zero_entropy_reranker.py

@@ -93,4 +93,5 @@ class ZeroEntropyReranker(BaseReranker):
             # Fallback to original order if reranking fails
             for doc in documents:
                 doc['rerank_score'] = 0.0
-            return documents[:top_k] if top_k else documents
+            final_top_k = top_k or self.config.top_k
+            return documents[:final_top_k] if final_top_k else documents