[5] Regarding the problem that the node spacing is halved after the collapse-expand event or expandElement is expanded in the polyline setting

### Describe the bug / 问题描述

当我设置了nodeSep，和rankSep 值为100 时，collapse-expand事件或者expandElement展开事件后，节点之间的间距变成一半了变成50了

### Reproduction link / 重现链接

_No response_

### Steps to Reproduce the Bug or Issue / 重现步骤

https://github.com/user-attachments/assets/1b900fec-8172-4d50-bbd4-8291d69bfe1a

### G6 Version / G6 版本

🆕 5.x

### Operating System / 操作系统

Windows

### Browser / 浏览器

Chrome

### Additional context / 补充说明

_No response_

Start by reproducing the linked example in G6 5.x with the polyline setting, nodeSep 100, and rankSep 100. Trace the collapse-expand and expandElement paths, then verify that node spacing remains 100 after either event on Windows Chrome.

Written by the indexing model from the issue text.