fix(android): derive artist tile cover from first cached album

Library + Home artist tiles were blank: cached_artists stores no cover and the sync payload (SyncArtistWire) carries none. Mirror Flutter's artistTileProvider JOIN — ArtistRef gains coverAlbumId + a displayCoverUrl getter; LibraryRepository.observeArtists and MetadataProvider.observeArtist combine artists with albums to supply the first album (by sort title) as the cover source. ArtistCard renders displayCoverUrl through ServerImage. Updated LibraryRepositoryTest to stub albumDao.observeAll so combine emits.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

android/app/src/main/java/com/fabledsword/minstrel/library/data/LibraryMappers.kt

@@ -64,11 +64,12 @@ fun AlbumDetailWire.toAlbumEntity(): CachedAlbumEntity =
 // source of truth for cache-first reads; mapping to a domain type here
 // keeps Room types out of the UI layer.
 
-fun CachedArtistEntity.toDomain(): ArtistRef =
+fun CachedArtistEntity.toDomain(coverAlbumId: String = ""): ArtistRef =
     ArtistRef(
         id = id,
         name = name,
         sortName = sortName,
+        coverAlbumId = coverAlbumId,
     )
 
 fun CachedAlbumEntity.toDomain(artistName: String = ""): AlbumRef =

android/app/src/main/java/com/fabledsword/minstrel/library/data/LibraryRepository.kt

@@ -10,6 +10,7 @@ import com.fabledsword.minstrel.models.ArtistDetailRef
 import com.fabledsword.minstrel.models.ArtistRef
 import com.fabledsword.minstrel.models.TrackRef
 import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.map
 import retrofit2.Retrofit
 import retrofit2.create
@@ -43,8 +44,17 @@ class LibraryRepository @Inject constructor(
 
     // ---- Reads (Flow, cache-first; the cache is the source of truth) ----
 
+    // Joins each artist to its first cached album (by sort title) so the
+    // tile cover derives from /api/albums/{id}/cover — cached_artists
+    // stores no cover and sync carries none. Mirrors Flutter's
+    // artistTileProvider JOIN.
     fun observeArtists(): Flow<List<ArtistRef>> =
-        artistDao.observeAll().map { rows -> rows.map { it.toDomain() } }
+        combine(artistDao.observeAll(), albumDao.observeAll()) { artists, albums ->
+            val firstAlbumByArtist = albums
+                .groupBy { it.artistId }
+                .mapValues { (_, list) -> list.minByOrNull { it.sortTitle }?.id ?: "" }
+            artists.map { it.toDomain(coverAlbumId = firstAlbumByArtist[it.id] ?: "") }
+        }
 
     fun observeAlbums(): Flow<List<AlbumRef>> =
         albumDao.observeAll().map { rows -> rows.map { it.toDomain() } }

android/app/src/main/java/com/fabledsword/minstrel/library/widgets/ArtistCard.kt

@@ -19,15 +19,14 @@ import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
 import androidx.compose.ui.graphics.Color
-import androidx.compose.ui.layout.ContentScale
 import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.text.style.TextOverflow
 import androidx.compose.ui.unit.dp
-import coil3.compose.AsyncImage
 import com.composables.icons.lucide.Lucide
 import com.composables.icons.lucide.User
 import com.fabledsword.minstrel.models.ArtistRef
 import com.fabledsword.minstrel.nav.LocalDetailSeedCache
+import com.fabledsword.minstrel.shared.widgets.ServerImage
 
 /**
  * One artist tile. Circular cover; name centered beneath. Tap fires
@@ -61,20 +60,17 @@ fun ArtistCard(
                     .clip(CircleShape),
                 contentAlignment = Alignment.Center,
             ) {
-                if (artist.coverUrl.isEmpty()) {
+                ServerImage(
+                    url = artist.displayCoverUrl,
+                    contentDescription = artist.name,
+                    modifier = Modifier.fillMaxSize(),
+                ) {
                     Icon(
                         imageVector = Lucide.User,
                         contentDescription = null,
                         tint = MaterialTheme.colorScheme.onSurfaceVariant,
                         modifier = Modifier.size(56.dp),
                     )
-                } else {
-                    AsyncImage(
-                        model = artist.coverUrl,
-                        contentDescription = artist.name,
-                        modifier = Modifier.fillMaxSize(),
-                        contentScale = ContentScale.Crop,
-                    )
                 }
             }
             Spacer(Modifier.height(8.dp))

android/app/src/main/java/com/fabledsword/minstrel/metadata/MetadataProvider.kt

@@ -12,6 +12,7 @@ import com.fabledsword.minstrel.models.TrackRef
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.onEach
 import kotlinx.coroutines.launch
@@ -70,9 +71,12 @@ class MetadataProvider @Inject constructor(
             .onEach { row -> if (row == null) fetchAlbum(id) }
 
     fun observeArtist(id: String): Flow<ArtistRef?> =
-        artistDao.observeById(id)
-            .map { it?.toDomain() }
-            .onEach { row -> if (row == null) fetchArtist(id) }
+        combine(
+            artistDao.observeById(id),
+            albumDao.observeByArtist(id),
+        ) { artist, albums ->
+            artist?.toDomain(coverAlbumId = albums.minByOrNull { it.sortTitle }?.id ?: "")
+        }.onEach { row -> if (row == null) fetchArtist(id) }
 
     fun observeTrack(id: String): Flow<TrackRef?> =
         trackDao.observeById(id)

android/app/src/main/java/com/fabledsword/minstrel/models/ArtistRef.kt

@@ -14,4 +14,23 @@ data class ArtistRef(
     val sortName: String = "",
     val albumCount: Int = 0,
     val coverUrl: String = "",
-)
+    val coverAlbumId: String = "",
+) {
+    /**
+     * Cover URL the UI should render, or null when the artist has no
+     * representative cover. Prefers the server-provided `coverUrl`
+     * (relative, e.g. `/api/artists` ships it); otherwise derives the
+     * first cached album's `/api/albums/{id}/cover` via [coverAlbumId].
+     *
+     * The fallback matters because cached_artists stores no cover and
+     * the sync payload carries none — so for cache-sourced artist tiles
+     * we mirror Flutter's `artistTileProvider`, which JOINs the first
+     * album to supply the cover. Resolve through `ServerImage`.
+     */
+    val displayCoverUrl: String?
+        get() = when {
+            coverUrl.isNotEmpty() -> coverUrl
+            coverAlbumId.isNotEmpty() -> "/api/albums/$coverAlbumId/cover"
+            else -> null
+        }
+}

android/app/src/test/java/com/fabledsword/minstrel/library/data/LibraryRepositoryTest.kt

@@ -58,6 +58,9 @@ class LibraryRepositoryTest {
                     CachedArtistEntity(id = "a1", name = "Boards of Canada", sortName = "Boards of Canada"),
                 ),
             )
+        // observeArtists now combines with albums (to derive the tile
+        // cover from the first album); stub it so combine can emit.
+        every { albumDao.observeAll() } returns flowOf(emptyList())
         val repo = LibraryRepository(artistDao, albumDao, trackDao, retrofit)
 
         repo.observeArtists().test {