test(subdirectory): split AppLink tests into a tsx file with mock pattern

The AppLink tests in navigationUtils.test.ts failed in CI because
withApplicationRoot's `jest.resetModules()` corrupts
@testing-library/react's module graph when its dist files are re-imported
across the reset.

Move AppLink coverage into navigationUtils.AppLink.test.tsx using the
file-level `jest.mock('src/utils/getBootstrapData', ...)` pattern
(same as SliceHeaderControls.subdirectory.test.tsx) so it works without
resetModules. JSX form is back, render is straightforward.