musikr: indicate song name always known

app/src/main/java/org/oxycblt/musikr/Music.kt

@@ -242,6 +242,7 @@ sealed interface MusicParent : Music {
  * @author Alexander Capehart (OxygenCobalt)
  */
 interface Song : Music {
+    override val name: Name.Known
     /** The track number. Will be null if no valid track number was present in the metadata. */
     val track: Int?
     /** The [Disc] number. Will be null if no valid disc number was present in the metadata. */

app/src/main/java/org/oxycblt/musikr/tag/interpret/PreMusic.kt

@@ -34,7 +34,7 @@ import org.oxycblt.musikr.util.update
 
 data class PreSong(
     val musicBrainzId: UUID?,
-    val name: Name,
+    val name: Name.Known,
     val rawName: String,
     val track: Int?,
     val disc: Disc?,