Add a GitHub-style quick repo switcher: a caret next to the owner/repo
breadcrumb
opens a dropdown that lists and searches the current owner's
repositories and
navigates to the selected one. The current repository is marked with a
check, and
private/fork repos show an icon.
Also, fix various bugs in fomtantic dropdown remote query
## Screenshots
<img width="505" height="198" alt="image"
src="https://github.com/user-attachments/assets/9f673d1b-fe60-41f0-b9e2-b00dc43720b5"
/>
Fixes#38187
---------
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
bircni