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/storage/base_rag_storage.py

@@ -41,9 +41,9 @@ class BaseRAGStorage(ABC):
     def search(
         self,
         query: str,
-        limit: int = 3,
+        limit: int = 5,
         filter: dict[str, Any] | None = None,
-        score_threshold: float = 0.35,
+        score_threshold: float = 0.6,
     ) -> list[Any]:
         """Search for entries in the storage."""