Drop the iOS-grouped rounded card, per-row chevron, and oversized
metrics on macOS. Use tighter padding, smaller icon/title fonts,
uppercase section headers, and top/bottom dividers so the list reads
like a native grouped Mac list. Force .buttonStyle(.plain) on row
buttons/NavigationLinks and add .contentShape(Rectangle()) so the
full row is hit-testable without picking up macOS's default link
styling. iOS and tvOS unchanged.