Split-pane inbox shell: icon rail with unread indicator, a searchable conversation listbox you can walk with the arrow keys, and a reading pane where star, archive and delete all work, with undo. Collapses to one pane on phones with a back button, and the composer sends on ⌘+Enter so Enter still makes a new line.
pnpm dlx shadcn@latest add "https://hirael.com/r/app-shell-03.json"