gh-stack is impossible to install: API rate limit exceeded

```
% gh extension install github/gh-stack
could not check for binary extension: HTTP 403: API rate limit exceeded for A.B.C.D. (But here's the good news: Authenticated requests get a higher rate limit. Check out the documentation for more details.) (https://api.github.com/repos/github/gh-stack/releases/latest)
```

首先重現 `gh extension install github/gh-stack`，並檢查要求 `https://api.github.com/repos/github/gh-stack/releases/latest` 的安裝路徑。使用未經驗證的要求確認失敗模式，並定義預期行為；完成的標準是能夠在不發生此速率限制失敗的情況下安裝擴充功能。

由索引模型根據 Issue 內容生成。