test(lyrics): fix lyrics tests after parser consolidation

- Rewrite the YAML-fallback test to assert the correct design: a
  non-Lyricsfile .yaml sidecar returns as plain text and shadows
  lower-priority sources (rather than falling through to .lrc).
- Add LibraryPath + relative Path split to the three subsonic tests
  that read sidecar files via storage.For(), so they resolve against
  the correct fixtures directory.
- Register a no-op extractor in api_suite_test.go BeforeSuite so
  newLocalStorage does not fatal when storage.For is called during
  sidecar-lyrics tests.

core/lyrics/lyrics_test.go

@@ -225,7 +225,7 @@ var _ = Describe("Lyrics", func() {
 		}))
 	})
 
-	It("falls through generic YAML sidecars that are not Lyricsfile documents", func() {
+	It("returns a non-Lyricsfile YAML sidecar as plain text, shadowing lower-priority sources", func() {
 		dir, err := os.MkdirTemp("", "lyrics-yaml-fallback-*")
 		Expect(err).ToNot(HaveOccurred())
 		DeferCleanup(func() {
@@ -242,10 +242,14 @@ var _ = Describe("Lyrics", func() {
 			Path:        "song.mp3",
 		})
 
+		// ParseLyrics falls back to plain text for any suffix when the content
+		// doesn't match the structured format, so the .yaml hit is non-empty and
+		// shadows the lower-priority .lrc entirely.
 		Expect(err).To(BeNil())
 		Expect(list).To(HaveLen(1))
+		Expect(list[0].Synced).To(BeFalse())
 		Expect(list[0].Line).To(Equal([]model.Line{
-			{Start: new(int64(1000)), Value: "Fallback line"},
+			{Value: "title: not lyricsfile"},
 		}))
 	})