[Bug Report] 2.13.9 popup关闭按钮展示问题

### Reproduction Link

无

### Vant Version

2.13.9

### Describe the Bug

<img width="776" height="904" alt="Image" src="https://github.com/user-attachments/assets/8b10f8d2-9550-4732-8235-c6f2857b4d83" />
样式错乱 导致定位absolute丢失

### Reproduce Steps

vue2 使用van-popup组件

### Device / Browser

_No response_