* Add Apple Icon Composer source file
Store the .icon project file in design/cmux.icon so the icon can be
edited in Icon Composer and regenerated from source.
* Regenerate all app icons from Icon Composer
Use ictool to render light/dark icon PNGs from the .icon source file
with proper macOS padding. Updates AppIcon, AppIcon-Debug (with DEV
banner), AppIconLight, and AppIconDark imagesets. Adds AppIcon.icon
to the Xcode project as a resource.
* Address review: fix trailing newline, remove .icon from bundle
- Add trailing newline to icon.json files
- Remove AppIcon.icon from Copy Bundle Resources (design-time only)
