Replace the hand-written CharacterRepository fakes in the ViewModel and
UseCase unit tests with MockK mocks (coEvery / coVerify). This is a
deliberate showcase of MockK and intentionally diverges from the repo's
"prefer fakes over mocks" guidance.
- Add io.mockk:mockk 1.14.3 to the version catalog and the unit-test bundle;
add it explicitly to DomainModuleConventionPlugin (domain does not consume
the bundle).
- CharacterListViewModelTest: strict mockk, per-page coEvery stubs; the
paging/in-flight guards are expressed via coVerify(exactly = ...) and
coVerifyOrder instead of fake call counters.
- CharacterDetailViewModelTest: relaxed mockk so "missing id" needs no
stubbing; explicit coEvery elsewhere.
- GetCharactersPageUseCaseTest: mockk + coVerify replaces the inline fake.
- Move character()/characterDetails() fixtures to CharacterFixtures.kt and
delete FakeCharacterRepository.kt.
- NetworkCharacterRepositoryTest stays on Ktor MockEngine (MockK is for
Kotlin collaborator interfaces, not the HTTP transport).