promote only the active source, and let a partial artist delete

Third review round:

- `promote` read every source's rows, so a single inactive source with waiting
  rows could fill the window and starve the source in use: its songs stayed
  queued with no engine id, for good, through every tick. It now scopes to the
  active source, which is also the only one that can resolve a URL here.
- An artist with some songs downloaded offered only Download, because the more
  menu rendered `action()` rather than the actions the state offers. It renders
  the whole list now, so a partial artist gets Download and Delete.
- The hero's long press is only advertised when there is something to delete,
  instead of announcing a Delete it would ignore, and it declares a button role
  again after losing `IconButton`.
- The delete dialog uses the platform size formatter rather than a hand-rolled
  one, which also fixes 999_999 reading as "1000.0 kB".
- The poll warms artwork through the same helper reconcile uses.

app/src/main/kotlin/com/subtracks/data/repo/DownloadRepository.kt

@@ -133,7 +133,10 @@ class DownloadRepository(
      * without an engine id, and the next tick promotes it.
      */
     private suspend fun promote(): List<SongDownload> {
-        val rows = db.downloadDao().all()
+        // Only the active source is handed over: another source's rows cannot resolve a URL here,
+        // and counting them would fill the window and stall the source actually in use.
+        val sourceId = sourceRepository.activeSourceIdOnce() ?: return emptyList()
+        val rows = db.downloadDao().all().filter { it.sourceId == sourceId }
         val free = IN_FLIGHT_LIMIT - rows.count { it.status.isActive && it.engineId != null }
         if (free <= 0) return emptyList()
         val promoted = ArrayList<SongDownload>()
@@ -338,6 +341,11 @@ class DownloadRepository(
             storeArtwork(sourceId, cover, thumbnail = false)
             storeArtwork(sourceId, cover, thumbnail = true)
         }
+        song?.artistId?.let { artistId ->
+            db.libraryDao().artistOnce(sourceId, artistId)?.let { artist ->
+                sourceRepository.refreshArtistInfo(sourceId, artistId, artist.name, force = false)
+            }
+        }
     }
 
     private suspend fun storeArtwork(
@@ -509,9 +517,7 @@ class DownloadRepository(
                         }
                     // Fetching artwork here would hold up the next tick, and with it the progress
                     // the queue is mirrored from.
-                    promoted.groupBy { it.sourceId }.forEach { (sourceId, rows) ->
-                        scope.launch { fetchArtworkSafely(sourceId, rows.map { it.songId }) }
-                    }
+                    scope.launch { warmArtwork(promoted) }
                 }
             }
     }

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

@@ -1,20 +1,12 @@
 package com.subtracks.ui.components
 
+import android.content.Context
+import android.text.format.Formatter
 import androidx.compose.material3.AlertDialog
 import androidx.compose.material3.Text
 import androidx.compose.material3.TextButton
 import androidx.compose.runtime.Composable
-
-fun formatBytes(bytes: Long): String {
-    val units = listOf("B", "kB", "MB", "GB", "TB")
-    var value = bytes.toDouble()
-    var unit = 0
-    while (value >= 1000 && unit < units.lastIndex) {
-        value /= 1000
-        unit++
-    }
-    return if (unit == 0) "$bytes ${units[unit]}" else "${"%.1f".format(value)} ${units[unit]}"
-}
+import androidx.compose.ui.platform.LocalContext
 
 @Composable
 fun DeleteDownloadsDialog(
@@ -26,7 +18,7 @@ fun DeleteDownloadsDialog(
     AlertDialog(
         onDismissRequest = onDismiss,
         title = { Text("Delete downloads") },
-        text = { Text("Delete the downloaded songs of \"$name\"? This frees ${formatBytes(bytes)}.") },
+        text = { Text("Delete the downloaded songs of \"$name\"? This frees ${formatBytes(LocalContext.current, bytes)}.") },
         confirmButton = {
             TextButton(
                 onClick = {
@@ -38,3 +30,8 @@ fun DeleteDownloadsDialog(
         dismissButton = { TextButton(onClick = onDismiss) { Text("Cancel") } },
     )
 }
+
+private fun formatBytes(
+    context: Context,
+    bytes: Long,
+): String = Formatter.formatFileSize(context, bytes)

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

@@ -62,6 +62,7 @@ import androidx.compose.ui.layout.onGloballyPositioned
 import androidx.compose.ui.layout.onSizeChanged
 import androidx.compose.ui.layout.positionInParent
 import androidx.compose.ui.platform.LocalDensity
+import androidx.compose.ui.semantics.Role
 import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.text.style.TextOverflow
 import androidx.compose.ui.unit.Dp
@@ -297,6 +298,8 @@ fun HeroHeader(
             modifier = controlsModifier.fillMaxWidth(),
             verticalAlignment = Alignment.CenterVertically,
         ) {
+            val action = downloadStatus.action()
+            val canDelete = BulkDownloadAction.Delete in downloadStatus.actions()
             Box(
                 modifier =
                     Modifier
@@ -304,18 +307,15 @@ fun HeroHeader(
                         .clip(CircleShape)
                         .combinedClickable(
                             enabled = hasSongs,
-                            onClick = { onDownloadAction(downloadStatus.action()) },
-                            onClickLabel = downloadActionLabel(downloadStatus.action()),
-                            onLongClick = {
-                                if (BulkDownloadAction.Delete in downloadStatus.actions()) {
-                                    onDownloadAction(BulkDownloadAction.Delete)
-                                }
-                            },
-                            onLongClickLabel = "Delete download",
+                            role = Role.Button,
+                            onClick = { onDownloadAction(action) },
+                            onClickLabel = downloadActionLabel(action),
+                            onLongClick = if (canDelete) ({ onDownloadAction(BulkDownloadAction.Delete) }) else null,
+                            onLongClickLabel = if (canDelete) "Delete download" else null,
                         ),
                 contentAlignment = Alignment.Center,
             ) {
-                when (downloadStatus.action()) {
+                when (action) {
                     BulkDownloadAction.Delete -> {
                         Icon(
                             imageVector = Icons.Rounded.DownloadDone,

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

@@ -332,22 +332,24 @@ private fun BulkDownloadItem(
     actions: ItemActions,
     dismiss: (() -> Unit) -> Unit,
 ) {
-    when ((download ?: ListDownloadStatus()).action()) {
-        BulkDownloadAction.Delete -> {
-            actions.deleteArtistDownload?.let { delete ->
-                MenuItem(Icons.Rounded.Delete, "Delete downloads") { dismiss { delete(artist) } }
+    for (action in (download ?: ListDownloadStatus()).actions()) {
+        when (action) {
+            BulkDownloadAction.Delete -> {
+                actions.deleteArtistDownload?.let { delete ->
+                    MenuItem(Icons.Rounded.Delete, "Delete downloads") { dismiss { delete(artist) } }
+                }
             }
-        }
 
-        BulkDownloadAction.Cancel -> {
-            actions.cancelArtistDownload?.let { cancel ->
-                MenuItem(Icons.Rounded.Cancel, "Cancel downloads") { dismiss { cancel(artist) } }
+            BulkDownloadAction.Cancel -> {
+                actions.cancelArtistDownload?.let { cancel ->
+                    MenuItem(Icons.Rounded.Cancel, "Cancel downloads") { dismiss { cancel(artist) } }
+                }
             }
-        }
 
-        BulkDownloadAction.Download -> {
-            actions.downloadArtist?.let { start ->
-                MenuItem(Icons.Rounded.Download, "Download") { dismiss { start(artist) } }
+            BulkDownloadAction.Download -> {
+                actions.downloadArtist?.let { start ->
+                    MenuItem(Icons.Rounded.Download, "Download") { dismiss { start(artist) } }
+                }
             }
         }
     }