brpc window 的数值异常

**Describe the bug (描述bug)**
我使用了 window 来监控测试流量，发现当测试流量为 2w 时，brpc window 的打点数值是正常的（通过 prometheus 观察），但是当测试流量上升到 5w 左右时，brpc window 的打点数值会出现异常，显示为 20w（通过 prometheus 观察）。怀疑和内部的数值类型设置有关，例如使用了 int16_t 的类型。但是在内部没有找到。想问下这个 case 可能的原因。

**To Reproduce (复现方法)**

**Expected behavior (期望行为)**

**Versions (各种版本)**
OS:
Compiler:
brpc:
protobuf:

**Additional context/screenshots (更多上下文/截图)**

Start by reproducing the brpc window metrics at roughly 20,000 and 50,000 test traffic while observing them through Prometheus. Check the window metric path and its numeric handling to determine why the reported value reaches about 200,000. Done means the cause is identified and a verified correction or clear diagnosis is provided.

Written by the indexing model from the issue text.