`gh stack submit` does not respect org-wide PR template

My organisation has an org-wide PR template, just as the one described here: https://github.com/orgs/community/discussions/183776. We used to have these templates in each repo, but they were all the same and repetitve, so we decided to define them in one place. We'd rather not go back to per-repo template.

Unfortunately, `gh stack submit` does not seem to respect them. User has two options with this command:
* By default it opens CLI dialog to enter PR's title and description. It doesn't use the org template
* `--auto` creates PR with some pre-populated footer and nothing else. Again no template is used.

The command supports repo-wide templates, thanks to https://github.com/github/gh-stack/pull/77, but this PR does not seem to take org-wide templates into account.

首先跟踪 `gh stack submit` 入口点及其默认对话框和 `--auto` 路径，并以 github/gh-stack pull request #77 作为仓库范围模板的上下文。使用组织范围的 PR 模板复现这两种模式，然后验证生成的 pull request 包含该模板，同时保留现有的 footer。

由索引模型根据 Issue 内容生成。