eframe sets the app icon at runtime, and on macOS that replaces the
Dock icon with a raw bitmap (the 256 px PNG we passed, or egui's logo
when none is given), which skips the system's icon treatment. Pass the
empty icon on macOS so eframe leaves the bundle's .icns alone.
Fixes#32.
Co-authored-by: Claude Opus 5.5 <[email protected]>
