- Remove the 'you only log in once per machine' claim from spotify.md
and document the ~6-month refresh token expiry with re-auth instructions
- Add test_client_wraps_invalid_grant_as_spotify_auth_required_error to
confirm SpotifyClient wraps AuthError(code=spotify_refresh_invalid_grant)
into SpotifyAuthRequiredError with a user-facing message
Refs: #28155