fix(scanner): apply split exceptions when per-tag Split overrides participant tags

Per-tag Tags.<name>.Split makes the generic ingestion path split the tag
before participant mapping runs, bypassing the whitelist. Attach the
exceptions to participant tag mappings (including sort variants) in clean().

model/metadata/metadata.go

@@ -205,6 +205,7 @@ func clean(filePath string, tags model.RawTags) model.Tags {
 	cleaned := make(model.Tags, len(mappings))
 
 	for name, mapping := range mappings {
+		mapping = mapping.WithParticipantExceptions(name)
 		var values []string
 		switch mapping.Type {
 		case model.TagTypePair:

model/tag_mappings.go

@@ -151,6 +151,33 @@ func ArtistSplitExceptionsRx() *regexp.Regexp {
 	return c.rx
 }
 
+// participantTagNames are the tags that hold artist names (or their sort
+// values), where split exceptions apply.
+var participantTagNames = sync.OnceValue(func() map[TagName]struct{} {
+	names := []TagName{
+		TagTrackArtist, TagTrackArtists, TagTrackArtistSort, TagTrackArtistsSort,
+		TagAlbumArtist, TagAlbumArtists, TagAlbumArtistSort, TagAlbumArtistsSort,
+	}
+	set := make(map[TagName]struct{}, len(names)+2*len(AllRoles))
+	for _, n := range names {
+		set[n] = struct{}{}
+	}
+	for role := range AllRoles {
+		set[TagName(role)] = struct{}{}
+		set[TagName(role+"sort")] = struct{}{}
+	}
+	return set
+})
+
+// WithParticipantExceptions returns the conf with the global artist split
+// exceptions attached when name is a participant (artist/role) tag.
+func (c TagConf) WithParticipantExceptions(name TagName) TagConf {
+	if _, ok := participantTagNames()[name]; ok {
+		c.ExceptionsRx = ArtistSplitExceptionsRx()
+	}
+	return c
+}
+
 type TagType string
 
 const (

model/tag_mappings_test.go

@@ -172,4 +172,23 @@ var _ = Describe("TagConf", func() {
 			Expect(second.MatchString("AC/DC")).To(BeTrue())
 		})
 	})
+
+	Describe("WithParticipantExceptions", func() {
+		BeforeEach(func() {
+			DeferCleanup(configtest.SetupConfig())
+			conf.Server.Scanner.ArtistSplitExceptions = []string{"Iron and Wine"}
+		})
+
+		It("attaches the exceptions regex to participant tags", func() {
+			for _, tag := range []TagName{"artist", "albumartist", "artists", "artistsort", "composer", "lyricist", "composersort"} {
+				Expect(TagConf{}.WithParticipantExceptions(tag).ExceptionsRx).ToNot(BeNil(), string(tag))
+			}
+		})
+
+		It("does not attach the exceptions regex to non-participant tags", func() {
+			for _, tag := range []TagName{"genre", "mood", "title", "releasetype"} {
+				Expect(TagConf{}.WithParticipantExceptions(tag).ExceptionsRx).To(BeNil(), string(tag))
+			}
+		})
+	})
 })