feat: multi-artist support in NowPlaying (OpenSubsonic artists array)

- Song model: add SongArtist{id,name} + artists: List<SongArtist>
  Navidrome sends this via OpenSubsonic extension — previously ignored
- NowPlaying: if song.artists has >1 entry, render each name as an
  inline AnnotatedString with ClickableText, separated by ' · ';
  every artist navigates to their own page with their real ID
  Falls back to single artist/artistId entry when array is absent
- AppNavigation: onArtistClick now receives artistId: String instead
  of a fixed closure, enabling per-artist navigation from the sheet

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

android/app/src/main/kotlin/com/novasonic/app/api/model/Models.kt

@@ -40,6 +40,12 @@ data class SubsonicError(val code: Int, val message: String)
 
 // ── Domain models ─────────────────────────────────────────────────────────────
 
+@Serializable
+data class SongArtist(
+    val id: String = "",
+    val name: String = "",
+)
+
 @Serializable
 data class Song(
     val id: String,
@@ -48,6 +54,7 @@ data class Song(
     val albumId: String? = null,
     val artist: String? = null,
     val artistId: String? = null,
+    val artists: List<SongArtist> = emptyList(),
     val track: Int? = null,
     val year: Int? = null,
     val genre: String? = null,

android/app/src/main/kotlin/com/novasonic/app/ui/AppNavigation.kt

@@ -324,11 +324,9 @@ fun AppNavigation() {
                 onShowOptions = {
                     playerState.currentSong?.let { s -> contextMenuSong = s }
                 },
-                onArtistClick = playerState.currentSong?.artistId?.let { artistId ->
-                    {
-                        showNowPlaying = false
-                        navController.navigate("artist/$artistId")
-                    }
+                onArtistClick = { artistId ->
+                    showNowPlaying = false
+                    if (artistId.isNotBlank()) navController.navigate("artist/$artistId")
                 },
             )
         }

android/app/src/main/kotlin/com/novasonic/app/ui/screen/NowPlayingScreen.kt

@@ -33,9 +33,14 @@ import androidx.compose.ui.layout.ContentScale
 import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.platform.LocalDensity
 import coil.request.ImageRequest
+import androidx.compose.ui.text.AnnotatedString
+import androidx.compose.ui.text.SpanStyle
+import androidx.compose.ui.text.buildAnnotatedString
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.text.style.TextOverflow
+import androidx.compose.ui.text.withStyle
+import androidx.compose.foundation.text.ClickableText
 import androidx.compose.ui.unit.Dp
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.sp
@@ -59,7 +64,7 @@ fun NowPlayingScreen(
     onDismiss: () -> Unit,
     onStarToggle: (() -> Unit)? = null,
     onShowOptions: (() -> Unit)? = null,
-    onArtistClick: (() -> Unit)? = null,
+    onArtistClick: ((artistId: String) -> Unit)? = null,
 ) {
     val song = state.currentSong
     var tab by remember { mutableStateOf(NpTab.PLAYER) }
@@ -208,16 +213,45 @@ fun NowPlayingScreen(
                                 maxLines = 1, overflow = TextOverflow.Ellipsis,
                             )
                             Spacer(Modifier.height(3.dp))
-                            if (!song?.artist.isNullOrBlank()) {
-                                Text(
-                                    song!!.artist!!,
-                                    fontFamily = Outfit, fontWeight = FontWeight.SemiBold,
-                                    fontSize = 15.sp, color = NsAccent,
-                                    maxLines = 1, overflow = TextOverflow.Ellipsis,
-                                    modifier = if (onArtistClick != null)
-                                        Modifier.clickable(onClick = onArtistClick)
-                                    else Modifier,
-                                )
+                            if (song != null && !song.artist.isNullOrBlank()) {
+                                // Build list: prefer song.artists (OpenSubsonic, has real IDs for all),
+                                // fall back to single entry from artist/artistId
+                                val artistList = if (song.artists.size > 1) song.artists
+                                    else listOf(com.novasonic.app.api.model.SongArtist(
+                                        id = song.artistId ?: "", name = song.artist!!))
+
+                                if (onArtistClick != null) {
+                                    val annotated = buildAnnotatedString {
+                                        artistList.forEachIndexed { idx, a ->
+                                            if (idx > 0) {
+                                                withStyle(SpanStyle(color = Color.White.copy(0.4f),
+                                                    fontFamily = Outfit, fontSize = 15.sp)) { append(" · ") }
+                                            }
+                                            pushStringAnnotation("ARTIST_ID", a.id)
+                                            withStyle(SpanStyle(color = NsAccent,
+                                                fontFamily = Outfit,
+                                                fontWeight = FontWeight.SemiBold,
+                                                fontSize = 15.sp)) { append(a.name) }
+                                            pop()
+                                        }
+                                    }
+                                    ClickableText(
+                                        text     = annotated,
+                                        maxLines = 2,
+                                        overflow = TextOverflow.Ellipsis,
+                                        onClick  = { offset ->
+                                            annotated.getStringAnnotations("ARTIST_ID", offset, offset)
+                                                .firstOrNull()?.let { onArtistClick(it.item) }
+                                        },
+                                    )
+                                } else {
+                                    Text(
+                                        song.artist!!,
+                                        fontFamily = Outfit, fontWeight = FontWeight.SemiBold,
+                                        fontSize = 15.sp, color = NsAccent,
+                                        maxLines = 2, overflow = TextOverflow.Ellipsis,
+                                    )
+                                }
                             }
                             if (!song?.album.isNullOrBlank()) {
                                 Text(