If AntvDarge uses a combo when the rankdir is LR, I want the nodes in the combo to be aligned on the same horizontal line.

### Describe the bug / 问题描述


### Reproduction link / 复现链接

https://stackblitz.com/edit/1vofigr5-jss7mbak?file=index.js

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

[https://stackblitz.com/edit/1vofigr5-jss7mbak?file=index.js](url)

### Version / 版本

🆕 5.x

### OS / 操作系统

- [ ] macOS
- [x] Windows
- [ ] Linux
- [ ] Others / 其他

### Browser / 浏览器

- [x] Chrome
- [ ] Edge
- [ ] Firefox
- [ ] Safari (Limited support / 有限支持)
- [ ] IE (Nonsupport / 不支持)
- [ ] Others / 其他

Start with the StackBlitz reproduction at index.js and run it to observe the combo layout with rankdir set to LR. Trace the layout behavior that positions combo nodes, then verify that the nodes align on one horizontal line in the reproduced case.

Written by the indexing model from the issue text.