refactor(metadata): drop per-file rawTags duplication for lyrics

mapLyrics() used a dedicated rawPairs()/rawTags path solely to bypass the
32KB lyrics truncation cap (the comment claiming sanitization "strips XML"
was inaccurate -- pair-type tags are only truncated, never stripped). That
duplicated every file s tags into a second lowercased map on the scan hot
path.

Instead, raise the lyrics maxLength so the normal Pairs() path keeps large
word-timed TTML/Enhanced-LRC intact, and remove rawTags/rawPairs. The
existing ">32KB embedded TTML" test continues to pass through Pairs().

model/metadata/map_mediafile.go

@@ -135,7 +135,7 @@ func (md Metadata) mapGain(rg, r128 model.TagName) *float64 {
 }
 
 func (md Metadata) mapLyrics() string {
-	rawLyrics := md.rawPairs(model.TagLyrics)
+	rawLyrics := md.Pairs(model.TagLyrics)
 
 	lyricList := make(model.LyricList, 0, len(rawLyrics))
 

model/metadata/metadata.go

@@ -70,7 +70,6 @@ func New(filePath string, info Info) Metadata {
 	return Metadata{
 		filePath:   filePath,
 		fileInfo:   info.FileInfo,
-		rawTags:    lowerTags(info.Tags),
 		tags:       clean(filePath, info.Tags),
 		audioProps: info.AudioProperties,
 		hasPicture: info.HasPicture,
@@ -80,7 +79,6 @@ func New(filePath string, info Info) Metadata {
 type Metadata struct {
 	filePath   string
 	fileInfo   FileInfo
-	rawTags    model.Tags
 	tags       model.Tags
 	audioProps AudioProperties
 	hasPicture bool
@@ -116,14 +114,6 @@ func (md Metadata) Pairs(key model.TagName) []Pair {
 	values := md.tags[key]
 	return slice.Map(values, func(v string) Pair { return Pair(v) })
 }
-func (md Metadata) rawPairs(key model.TagName) []Pair {
-	mapping, ok := model.TagMappings()[key]
-	if !ok {
-		return nil
-	}
-	values := filterDuplicatedOrEmptyValues(processPairMapping(key, mapping, md.rawTags))
-	return slice.Map(values, func(v string) Pair { return Pair(v) })
-}
 func (md Metadata) first(key model.TagName) string {
 	if v, ok := md.tags[key]; ok && len(v) > 0 {
 		return v[0]

model/metadata/metadata_test.go

@@ -105,7 +105,7 @@ var _ = Describe("Metadata", func() {
 				props.Tags = model.RawTags{
 					"Title":      {strings.Repeat("a", 2048)},
 					"Comment":    {strings.Repeat("a", 8192)},
-					"lyrics:xxx": {strings.Repeat("a", 60000)},
+					"lyrics:xxx": {strings.Repeat("a", 2_000_000)},
 				}
 				md = metadata.New(filePath, props)
 
@@ -116,9 +116,21 @@ var _ = Describe("Metadata", func() {
 				Expect(pair).To(HaveLen(1))
 				Expect(pair[0].Key()).To(Equal("xxx"))
 
+				// Lyrics keep a much larger cap so word-timed karaoke survives.
 				// Note: a total of 6 characters are lost from maxLength from
-				// the key portion and separator
-				Expect(pair[0].Value()).To(HaveLen(32762))
+				// the key portion and separator.
+				Expect(pair[0].Value()).To(HaveLen(1048570))
+			})
+
+			It("keeps embedded lyrics that exceed the old 32KB cap", func() {
+				props.Tags = model.RawTags{
+					"lyrics:xxx": {strings.Repeat("a", 60000)},
+				}
+				md = metadata.New(filePath, props)
+
+				pair := md.Pairs(model.TagLyrics)
+				Expect(pair).To(HaveLen(1))
+				Expect(pair[0].Value()).To(HaveLen(60000))
 			})
 
 			It("should split multiple values", func() {

resources/mappings.yaml

@@ -110,7 +110,9 @@ main:
   lyrics:
     # Note, @lyr and wm/lyrics have been removed. Taglib somehow appears to always populate `lyrics:xxx`
     aliases: [ uslt:description, lyrics, unsyncedlyrics ]
-    maxLength: 32768
+    # Generous cap: word-timed TTML/Enhanced-LRC karaoke for a full song can run
+    # well past the previous 32KB limit. Still bounded to guard against pathological tags.
+    maxLength: 1048576
     type: pair # ex: lyrics:eng, lyrics:xxx
   comment:
     aliases: [ comm:description, comment, ©cmt, description, icmt ]