refactor(lyrics): fold parseLyricsfile into lyricParser signature and rename file

- parseLyricsfile now matches the lyricParser signature directly (reads via
  bytes.NewReader), removing the parseLyricsfileBytes adapter and the
  string(contents) copy; the lyricFormats table references it directly.
- StructuredLyrics drops the vestigial LyricList{} init (json.Unmarshal
  overwrites; MarshalJSON owns the empty->[] invariant).
- Rename lyricsfile.go -> lyrics_lyricsfile.go (and its test) to match the
  lyrics_<format>.go convention used by lrc/srt/ttml.

model/lyrics_lyricsfile.go

@@ -1,6 +1,7 @@
 package model
 
 import (
+	"bytes"
 	"fmt"
 	"strings"
 
@@ -19,9 +20,9 @@ import (
 // overlapping lines are attributed to synthetic voice agents via lowest-free
 // voice ID assignment so the OpenSubsonic v2 enhanced response can split
 // parallel vocals.
-func parseLyricsfile(text string) (LyricList, error) {
+func parseLyricsfile(_ string, contents []byte) (LyricList, error) {
 	var doc lyricsfileDocument
-	dec := yaml.NewDecoder(strings.NewReader(text))
+	dec := yaml.NewDecoder(bytes.NewReader(contents))
 	dec.KnownFields(false)
 	if err := dec.Decode(&doc); err != nil {
 		return nil, fmt.Errorf("not a valid Lyricsfile YAML: %w", err)

model/lyrics_lyricsfile_test.go

@@ -8,7 +8,7 @@ import (
 var _ = Describe("parseLyricsfile", func() {
 	DescribeTable("returns nil,nil for YAML without the Lyricsfile version marker",
 		func(input string) {
-			lyrics, err := parseLyricsfile(input)
+			lyrics, err := parseLyricsfile("", []byte(input))
 			Expect(err).ToNot(HaveOccurred())
 			Expect(lyrics).To(BeNil())
 		},
@@ -22,7 +22,7 @@ lines:
 	)
 
 	It("returns an error for invalid YAML", func() {
-		_, err := parseLyricsfile("not: valid: yaml: [")
+		_, err := parseLyricsfile("", []byte("not: valid: yaml: ["))
 		Expect(err).To(HaveOccurred())
 	})
 
@@ -39,7 +39,7 @@ lines:
   - text: "You know the rules and so do I"
     start_ms: 22801
 `
-		lyrics, err := parseLyricsfile(input)
+		lyrics, err := parseLyricsfile("", []byte(input))
 		Expect(err).ToNot(HaveOccurred())
 		Expect(lyrics).To(HaveLen(1))
 
@@ -79,7 +79,7 @@ plain: |
 
   Second line
 `
-		lyrics, err := parseLyricsfile(input)
+		lyrics, err := parseLyricsfile("", []byte(input))
 		Expect(err).ToNot(HaveOccurred())
 		Expect(lyrics).To(HaveLen(1))
 
@@ -115,7 +115,7 @@ lines:
         start_ms: 1500
         end_ms: 3000
 `
-		lyrics, err := parseLyricsfile(input)
+		lyrics, err := parseLyricsfile("", []byte(input))
 		Expect(err).ToNot(HaveOccurred())
 		Expect(lyrics).To(HaveLen(1))
 
@@ -167,7 +167,7 @@ lines:
         start_ms: 3000
         end_ms: 3500
 `
-		lyrics, err := parseLyricsfile(input)
+		lyrics, err := parseLyricsfile("", []byte(input))
 		Expect(err).ToNot(HaveOccurred())
 		Expect(lyrics).To(HaveLen(1))
 
@@ -206,7 +206,7 @@ lines:
         start_ms: 2000
         end_ms: 3000
 `
-		lyrics, err := parseLyricsfile(input)
+		lyrics, err := parseLyricsfile("", []byte(input))
 		Expect(err).ToNot(HaveOccurred())
 		Expect(lyrics).To(HaveLen(1))
 
@@ -245,7 +245,7 @@ metadata:
   language: 'eng'
   instrumental: true
 `
-		lyrics, err := parseLyricsfile(input)
+		lyrics, err := parseLyricsfile("", []byte(input))
 		Expect(err).ToNot(HaveOccurred())
 		Expect(lyrics).To(HaveLen(1))
 
@@ -269,7 +269,7 @@ lines:
     start_ms: 2000
     end_ms: 3000
 `
-		lyrics, err := parseLyricsfile(input)
+		lyrics, err := parseLyricsfile("", []byte(input))
 		Expect(err).ToNot(HaveOccurred())
 		Expect(lyrics).To(HaveLen(1))
 

model/lyrics_parse.go

@@ -14,10 +14,6 @@ import (
 // do not carry their own.
 type lyricParser func(lang string, contents []byte) (LyricList, error)
 
-func parseLyricsfileBytes(_ string, contents []byte) (LyricList, error) {
-	return parseLyricsfile(string(contents))
-}
-
 // lyricFormats is the structured formats in content-sniff probe order; each
 // row's suffixes drive sidecar dispatch. LRC/plain is the unlisted fallback floor.
 var lyricFormats = []struct {
@@ -26,7 +22,7 @@ var lyricFormats = []struct {
 }{
 	{[]string{".ttml"}, parseTTMLWithDefaultLang},
 	{[]string{".srt"}, parseSRTWithLanguage},
-	{[]string{".yaml", ".yml"}, parseLyricsfileBytes},
+	{[]string{".yaml", ".yml"}, parseLyricsfile},
 }
 
 // ParseLyrics is the single entry point for parsing lyrics. A known suffix routes

model/mediafile.go

@@ -138,7 +138,7 @@ func (mf MediaFile) AlbumCoverArtID() ArtworkID {
 }
 
 func (mf MediaFile) StructuredLyrics() (LyricList, error) {
-	lyrics := LyricList{}
+	var lyrics LyricList
 	err := json.Unmarshal([]byte(mf.Lyrics), &lyrics)
 	if err != nil {
 		return nil, err