Add a lightweight custom i18n system supporting English (default)
and Chinese, with a language switcher in Settings > General.
All 35+ UI components internationalized with ~270 translation keys,
including 189 Chinese spinner verbs and server error code mapping.
- Input @ in composer to open file search popup showing project root
- Filter files/directories by typing, navigate with keyboard or mouse
- Click directory to enter subdirectory, type / to navigate deeper
- Enter selects item and inserts path text at cursor, popup closes
- Parse filter path (e.g. @src/components/) to auto-navigate and search
- Desktop: filesystem browse/search API supports includeFiles and search
- Web: directory tree browser with real-time search filtering
