make the now playing art and artist names tap targets

Tapping the cover art on now playing opens its album and tapping the artist name opens
the artist, matching the context menu actions; the album detail subtitle does the same
for its artist. Both are inert when the queue item has no album/artist id.

Artist detail's album cells also stop drawing the letter placeholder underneath: with a
thumbnail underlay and the full image on top, the letter only showed because the default
`showPlaceholder = true` was left on, so a cold cell flashed a letter before the art.
They now match the hero's `showPlaceholder = art == null`.

app/src/main/kotlin/com/subtracks/ui/components/HeroDetailScaffold.kt

@@ -201,6 +201,7 @@ fun HeroHeader(
     controlsModifier: Modifier = Modifier,
     thumbnailRef: CoverArtRef? = null,
     comment: String? = null,
+    onSubtitleClick: (() -> Unit)? = null,
     modifier: Modifier = Modifier,
 ) {
     Column(
@@ -235,6 +236,7 @@ fun HeroHeader(
                 textAlign = TextAlign.Center,
                 maxLines = 2,
                 overflow = TextOverflow.Ellipsis,
+                modifier = if (onSubtitleClick != null) Modifier.clickable { onSubtitleClick() } else Modifier,
             )
         }
         if (!comment.isNullOrBlank()) {

app/src/main/kotlin/com/subtracks/ui/library/AlbumDetailScreen.kt

@@ -80,6 +80,11 @@ fun AlbumDetailRoute(
         onShuffle = viewModel::shuffle,
         onPlay = viewModel::playAll,
         onMore = { album?.let { contextMenuHost?.show(MenuTarget.Album(it, viewModel.coverArt(it.coverArt, true)), actions) } },
+        onArtistClick =
+            album
+                ?.takeIf { !it.albumArtist.isNullOrBlank() }
+                ?.let { it.artistId }
+                ?.let { id -> { onViewArtist(id) } },
         playingSongId = playback.item?.id.takeIf { context?.kind == QueueKind.Album && context.refId == albumId },
     )
 }
@@ -98,6 +103,7 @@ fun AlbumDetailScreen(
     onPlay: () -> Unit = { onSongClick(0) },
     onDownload: () -> Unit = {},
     onMore: () -> Unit = {},
+    onArtistClick: (() -> Unit)? = null,
     playingSongId: String? = null,
     modifier: Modifier = Modifier,
 ) {
@@ -124,15 +130,17 @@ fun AlbumDetailScreen(
         title = album?.name.orEmpty(),
         onBack = onBack,
         header = { controlsModifier, topInset ->
+            val artistName = album?.albumArtist?.takeIf { it.isNotBlank() }
             HeroHeader(
                 art = coverArt(album?.coverArt, false),
                 thumbnailRef = coverArt(album?.coverArt, true),
                 name = album?.name.orEmpty(),
                 subtitle =
                     listOfNotNull(
-                        album?.albumArtist?.takeIf { it.isNotBlank() },
+                        artistName,
                         album?.year?.takeIf { it > 0 }?.toString(),
                     ).joinToString(" $DOT "),
+                onSubtitleClick = onArtistClick,
                 hasSongs = songs.isNotEmpty(),
                 onPlay = onPlay,
                 onShuffle = onShuffle,

app/src/main/kotlin/com/subtracks/ui/library/ArtistDetailScreen.kt

@@ -270,7 +270,9 @@ fun ArtistDetailScreen(
                         }
                     }
                     itemsIndexed(albums, key = { _, album -> album.id }) { index, album ->
-                        PrefetchArtworkSeeds(coverArt(album.coverArt, true))
+                        val art = coverArt(album.coverArt, false)
+                        val thumbnail = coverArt(album.coverArt, true)
+                        PrefetchArtworkSeeds(thumbnail)
                         Column(
                             modifier =
                                 Modifier
@@ -279,14 +281,15 @@ fun ArtistDetailScreen(
                                         end = if (index % 2 == 1) 16.dp else 0.dp,
                                     ).combinedClickable(
                                         onClick = { onAlbumClick(album) },
-                                        onLongClick = { onAlbumLongClick(MenuTarget.Album(album, coverArt(album.coverArt, true))) },
+                                        onLongClick = { onAlbumLongClick(MenuTarget.Album(album, thumbnail)) },
                                     ).onSizeChanged { albumHeightPx = it.height.toFloat() },
                         ) {
                             Box {
                                 CoverArt(
-                                    ref = coverArt(album.coverArt, false),
+                                    ref = art,
                                     name = album.name,
-                                    thumbnailRef = coverArt(album.coverArt, true),
+                                    thumbnailRef = thumbnail,
+                                    showPlaceholder = art == null,
                                     modifier = Modifier.fillMaxWidth().aspectRatio(1f).clip(RoundedCornerShape(2.dp)),
                                 )
                                 StarredBadge(

app/src/main/kotlin/com/subtracks/ui/playback/NowPlayingScreen.kt

@@ -3,6 +3,7 @@ package com.subtracks.ui.playback
 import android.content.Context
 import androidx.compose.foundation.background
 import androidx.compose.foundation.basicMarquee
+import androidx.compose.foundation.clickable
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
@@ -50,6 +51,7 @@ import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.platform.LocalDensity
+import androidx.compose.ui.platform.testTag
 import androidx.compose.ui.text.PlatformTextStyle
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.text.style.LineHeightStyle
@@ -80,6 +82,8 @@ import com.subtracks.ui.theme.HeroGradient
 import com.subtracks.ui.theme.rememberArtworkColors
 import org.koin.compose.koinInject
 
+const val NOW_PLAYING_COVER_TAG = "now-playing-cover"
+
 @Composable
 fun NowPlayingRoute(
     onBack: () -> Unit,
@@ -139,6 +143,8 @@ fun NowPlayingRoute(
         onShuffle = controller::toggleShuffle,
         onRepeat = controller::cycleRepeat,
         onMore = { song?.let { contextMenuHost?.show(MenuTarget.Song(it, thumbnail), actions) } },
+        onAlbumClick = song?.albumId?.let { id -> { onViewAlbum(id) } },
+        onArtistClick = song?.artistId?.let { id -> { onViewArtist(id) } },
         onSeek = controller::seekTo,
         modifier = modifier,
     )
@@ -182,6 +188,8 @@ fun NowPlayingScreen(
     onShuffle: () -> Unit = {},
     onRepeat: () -> Unit = {},
     onMore: () -> Unit = {},
+    onAlbumClick: (() -> Unit)? = null,
+    onArtistClick: (() -> Unit)? = null,
     onSeek: (Long) -> Unit,
     thumbnailRef: CoverArtRef? = null,
     modifier: Modifier = Modifier,
@@ -247,7 +255,13 @@ fun NowPlayingScreen(
                         horizontalAlignment = Alignment.CenterHorizontally,
                     ) {
                         Box(
-                            modifier = Modifier.weight(1f).fillMaxWidth().padding(top = 2.dp),
+                            modifier =
+                                Modifier
+                                    .weight(1f)
+                                    .fillMaxWidth()
+                                    .padding(top = 2.dp)
+                                    .clickable(enabled = onAlbumClick != null) { onAlbumClick?.invoke() }
+                                    .testTag(NOW_PLAYING_COVER_TAG),
                             contentAlignment = Alignment.Center,
                         ) {
                             CoverArt(
@@ -286,7 +300,13 @@ fun NowPlayingScreen(
                                     modifier = Modifier.basicMarquee(),
                                 )
                             }
-                            Box(Modifier.height(subtitleHeight), contentAlignment = Alignment.Center) {
+                            Box(
+                                modifier =
+                                    Modifier
+                                        .height(subtitleHeight)
+                                        .clickable(enabled = onArtistClick != null) { onArtistClick?.invoke() },
+                                contentAlignment = Alignment.Center,
+                            ) {
                                 Text(
                                     text = state.item?.artist.orEmpty(),
                                     style = subtitleStyle,