macos.rs already read pictures from NSPasteboard itself while arboard
wrapped the same pasteboard for text, pages and files, and pulled in
objc2-app-kit 0.3 beside the 0.2 the app uses. The other reads and the
write now go to NSPasteboard directly, as arboard made them, and arboard
stays for Windows and X11. A test round-trips text, a page and files
through a private pasteboard, leaving the user's alone.

Assisted-by: claude-opus-5.5