Replace the Swift squircle hack with the correct Apple approach:
generate a proper .icns using sips + iconutil, then replace
electron.icns in the Electron bundle before launch. macOS applies
its native squircle mask + shadow from the .icns automatically.
macOS only applies the squircle mask to packaged .app bundles. For dev
mode, generate a pre-masked icon-dock.png via Swift/AppKit at launch
and set it with app.dock.setIcon(). Silently skipped on non-macOS.
Jannis Braun