AppIcon.appiconset only defined an iOS "universal" 1024x1024 entry, so
the macOS build had no mac-idiom icon at all — App Store Connect
rejected uploads for missing the required 512pt@2x (1024x1024) image.
Generates the full mac icon set (16/32/128/256/512pt at 1x/2x) from
the existing 1024px source and wires it into Contents.json.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FXcrACM5sok3M1KQJ8kByy
