The "Add to list" panel now draws your lists as a folder tree.

It shows up wherever GitHub opens that panel: on a repository page, and on any repo row that carries a star button your feed, trending, and the stars tab.
Folders fold, remember whether they were open, and show how many lists they hold.

The tree also looks the same everywhere now. The stars tab, the list rail and both panels share one set of guide lines, and every color comes from GitHub's own theme tokens, so light and dark both follow your setting.

Fixed
- Rows no longer stretch when GitHub serves its doubled row padding every session gets the same height now.
- Popup width is pinned: Firefox sized it to max-content, Android opened it at full screen width.

Faster
- The list index is prefetched on a hard load of a list page and warmed from the stars tab DOM, so the rail paints without waiting on the fetch.