revert: 撤销假流式修改

backend/app/agent/agent_service.py

@@ -189,20 +189,6 @@ class AIAgentService:
                     }
         # 处理普通 token
         elif token_content:
-            # 如果内容较长，拆成单个字符模拟流式效果
-            if len(token_content) > 1:
-                import asyncio
-                for char in token_content:
-                    yield {
-                        "type": "llm_token",
-                        "node": node_name,
-                        "token": char,
-                        "reasoning_token": reasoning_token
-                    }
-                    # 短暂暂停，模拟打字效果
-                    await asyncio.sleep(0.01)
-            else:
-                # 内容较短，直接发送
             yield {
                 "type": "llm_token",
                 "node": node_name,