Cannot change the default base branch `main` (GraphQL: Cannot change the base branch because the pull request is part of a stack. (updatePullRequest))

This feature could be better for code management if it can be used for projects with multiple environments since I cannot change the default base branch `main` to other branches (like staging, or to break a branch into many features and merge into it for better testing)

I have tried the following
```
# In your local repo
gh pr edit --base
```
And I got
```
GraphQL: Cannot change the base branch because the pull request is part of a stack. (updatePullRequest)
```

I would love an update or explanation for this

首先使用 `gh pr edit --base ` 重現問題，並檢查回報的 `updatePullRequest` GraphQL 錯誤。確定堆疊的 pull request 是否支援變更基礎分支，然後記錄這項限制，或定義 staging 與多功能工作流程所需的行為。

由索引模型根據 Issue 內容生成。