Removing the old Retag Tool (d91e6a38) deleted core/library/retag.py but left
its tests behind. tests/library/test_retag.py imported the gone module at
module top, so pytest aborted collection of the ENTIRE suite (CI red on every
run). tests/test_lyrics_reembed_from_sidecar.py had two RetagDeps tests for the
same removed dataclass (lazy imports — would fail at runtime once collection
proceeded).
Delete the orphaned test file + drop the two dead RetagDeps tests (the rest of
the lyrics-sidecar file is unrelated and stays). Also drop a pointless
f-string in test_library_retag_job. Suite now collects all 5008 tests.
07801aeb5b