A runnable MVI screen (reached from the list overflow menu) that forces a real
DataError.Network case and routes it through the same pipeline a genuine call
uses: Result.Error -> onFailure -> DataError.toUiText() -> design-system
ErrorState. Three distinct cases (NO_INTERNET, NOT_FOUND, SERVER_ERROR) each
render their mapped message; Retry re-issues the last attempt via an Action; a
successful load clears the error. Wired as intra-feature navigation
(ErrorDemoRoute) and registered in Koin (incl. the UseCase factoryOf).