refactor(module-llm):优化知识库问答逻辑

-将 rateResult 的比较改为直接比较原始值 rate，提高代码可读性和性能
- 删除不必要的字符串转换和格式化操作，简化代码逻辑

yudao-module-llm/yudao-module-llm-biz/src/main/java/cn/iocoder/yudao/module/llm/service/conversation/ConversationServiceImpl.java

@@ -627,7 +627,7 @@ public class ConversationServiceImpl implements ConversationService {
             String rateResult = df.format(rate);
             log.info("{} 命中率: {}", "[KnowledgeBase]", rateResult);
 
-            if (StringUtils.isBlank(rateResult)||Double.parseDouble(rateResult)<=0.0){
+            if (StringUtils.isBlank(rateResult)||rate<=0.0){
                 return Collections.emptyList();
             }