max_body_size逻辑不一致

```
DEFINE_uint64(max_body_size, 64 * 1024 * 1024,
"Maximum size of a single message body in all protocols");
```

> A message from x.x.x.x:4096(protocol=baidu_std) is bigger than 67108864 bytes, the connection will be closed. Set max_body_size to allow bigger messages

看代码定义说是对所有协议生效，但在测试中发现用h2:grpc没有消息过大的报错，用baidu_std就会有上面的错误，是对h2:grpc不检测吗，这个设计是预期的还是漏了逻辑呢

搜了代码也没发现

Start with the max_body_size definition and trace how message-size checks are applied for baidu_std and h2:grpc. Compare the two protocol paths and any relevant tests or logs to determine whether the differing behavior is intentional. Done means documenting the expected behavior and aligning the implementation or reporting a confirmed design choice.

Written by the indexing model from the issue text.