The DRY pass audit (#375) found two inline mock patterns repeated across the
vitest suite: a default empty-playlists mock for $lib/api/playlists (4 exact
copies in menu/card tests) and an api-client spy mock for $lib/api/client
(9 callers split between get-only and full-RESTy shapes — unified into one
helper that always returns all four verb spies).
Mirrors the existing test-utils/mocks/likes.ts and test-utils/mocks/quarantine.ts
convention. Tests with intentionally divergent shapes (AddToPlaylistMenu's
richer createPlaylist payload, PlaylistCard's getPlaylist, route-specific
mocks, events.svelte's specific resolved value) stay inline.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Uses createArtistsQuery (infinite), URL-driven sort dropdown, Load
more pagination, delayed skeleton, and shared error banner. Also
introduces the test-utils/query.ts helpers for subsequent page tests.