feat: a version named after a dash counts as a version, and a song held twice beside a wrong slot no longer blocks it (M498)

- songKey drops a dashed version suffix (" - Instrumental Version", " - Radio
  Edit", live, remix, mix, acoustic, demo, reprise, rework, VIP), so Andora's
  "Goodbye Yesterday - Instrumental Version" is distinct, not a wrong slot.
- wrongSlots accepts several fitting copies when they share one title
  (Killjoy twice beside Dreamland): the other slot's copy is removed, and the
  doubled song is left for the next sweep to find as a pair the resolver merges.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/library/duplicate_classify.go

@@ -85,11 +85,18 @@ func ClassifyDuplicateGroup(tier string, members []ClassifyMember) DuplicateClas
 	}
 }
 
-// songKey is MatchTitleKey with every bracketed segment dropped: the song a
-// title names, whatever version of it. "Lovesick (Instrumental)" and
-// "Lovesick" share one.
+// versionSuffix is a version named after a dash rather than in brackets:
+// "Goodbye Yesterday - Instrumental Version", "Song - Radio Edit".
+var versionSuffix = regexp.MustCompile(
+	`(?i)\s-\s[^-]*\b(version|instrumental|remix|mix|live|acoustic|demo|edit|reprise|rework|vip)\b[^-]*$`)
+
+// songKey is MatchTitleKey with every bracketed segment and a dashed version
+// suffix dropped: the song a title names, whatever version of it.
+// "Lovesick (Instrumental)", "Lovesick - Instrumental Version" and "Lovesick"
+// share one.
 func songKey(title, artist string) string {
-	if key := MatchTitleKey(bracketed.ReplaceAllString(title, " "), artist); key != "" {
+	t := versionSuffix.ReplaceAllString(bracketed.ReplaceAllString(title, " "), "")
+	if key := MatchTitleKey(t, artist); key != "" {
 		return key
 	}
 	return MatchTitleKey(title, artist)