Cross-check
Core packages must compile for iOS and watchOS even when you developed on macOS.
./Scripts/crosscheck.sh ios
./Scripts/crosscheck.sh watchos
Failures usually mean an AppKit/UIKit import leaked into Packages/Diffuse* core, or an API that does not exist on that SDK.
Do not skip this to land a Mac-only type in Core. Put it in the app target or DiffuseCollectors behind the right registry.