feat: add configurable search parameters for RAG, knowledge, and memory (#3531)

- Add limit and score_threshold to BaseRagConfig, propagate to clients  
- Update default search params in RAG storage, knowledge, and memory (limit=5, threshold=0.6)  
- Fix linting (ruff, mypy, PERF203) and refactor save logic  
- Update tests for new defaults and ChromaDB behavior

src/crewai/rag/chromadb/factory.py

@@ -39,4 +39,6 @@ def create_client(config: ChromaDBConfig) -> ChromaDBClient:
     return ChromaDBClient(
         client=client,
         embedding_function=config.embedding_function,
+        default_limit=config.limit,
+        default_score_threshold=config.score_threshold,
     )