fix(dify-chat): 优化think标签内容解析逻辑

- 修复了think标签结束后的推理内容截取问题
- 添加了对think标签前后内容的分别处理
- 改进了消息构建器的内容拼接逻辑
- 确保think标签后的内容正确设置为message字段
- 优化了推理内容和消息内容的分离处理
- 修复了标签解析过程中的字符串索引计算问题

src/main/java/cn/com/poc/common/service/impl/DifyChatServiceImpl.java

@@ -203,9 +203,23 @@ public class DifyChatServiceImpl implements DifyChatService {
                                     largeModelDemandResult.setMessage(content);
                                 }
                             } else {
-                                largeModelDemandResult.setReasoningContent(
-                                        content.replaceFirst(THINK_END_TAG, StringUtils.EMPTY));
-                                isThink = !content.contains(THINK_END_TAG);
+                                if (content.contains(THINK_END_TAG)) {
+                                    String reasoningPart = content.substring(0, content.indexOf(THINK_END_TAG));
+                                    if (StringUtils.isNotEmpty(reasoningPart)) {
+                                        reasoningContentBuilder.append(reasoningPart);
+                                        largeModelDemandResult.setReasoningContent(reasoningPart);
+                                    }
+                                    // 处理think标签之后的内容
+                                    String afterThinkTag = content.substring(content.indexOf(THINK_END_TAG) + THINK_END_TAG.length());
+                                    if (StringUtils.isNotEmpty(afterThinkTag)) {
+                                        messageBuilder.append(afterThinkTag);
+                                        largeModelDemandResult.setMessage(afterThinkTag);
+                                    }
+                                    isThink = false;
+                                } else {
+                                    reasoningContentBuilder.append(content);
+                                    largeModelDemandResult.setReasoningContent(content);
+                                }
                             }
                             largeModelDemandResult.setCode("0");
                             sseUtil.send(JsonUtils.serialize(largeModelDemandResult));