fix: 使用终态答案校正流式输出

- DONE 事件携带后端汇总的完整最终正文

- 前端完成时替换可能受损的流式文本

- 补充文件 URL 终态校正回归测试

easyflow-ui-admin/app/src/views/ai/agent-chat/adapters/agentTimelineAdapter.test.ts

@@ -298,6 +298,38 @@ describe('agentTimelineAdapter', () => {
     });
   });
 
+  it('reconciles streamed text with the canonical final answer', () => {
+    const items: any[] = [];
+
+    for (const delta of [
+      'http://127.0.0.1:39',
+      '0',
+      '/easyflow/file.docx',
+    ]) {
+      applyAgentSseEnvelope(items, {
+        domain: 'LLM',
+        type: 'MESSAGE',
+        payload: { delta },
+      });
+    }
+    applyAgentSseEnvelope(items, {
+      domain: 'SYSTEM',
+      type: 'DONE',
+      payload: {
+        finalText: 'http://127.0.0.1:39000/easyflow/file.docx',
+      },
+    });
+
+    const assistant = items.find(
+      (item): item is ChatTimelineMessageItem =>
+        item.type === 'message' && item.role === 'assistant',
+    );
+    expect(assistant?.parts[0]?.content).toBe(
+      'http://127.0.0.1:39000/easyflow/file.docx',
+    );
+    expect(assistant?.status).toBe('done');
+  });
+
   it('applies streaming text, HITL approval and error envelopes', () => {
     const items: any[] = [];