address review: fix reveal anchoring and ID3v1 names

RevealNewFrontItem compared the post-anchor firstVisibleItemIndex against the
front threshold, so it only worked when the row was at index 0 and exactly one
item was prepended. Recover the pre-change position by subtracting the number
of items now before the old front, and cover the one-in and multi-prepend cases
with integration tests.

Adopt the canonical TagLib/mutagen names for two extended indices: 133 is
Worldbeat (was Negerpunk) and 148 is Abstract (was Christmas). Drop the unused
default on SongInfoDialog's genres argument.

app/src/main/kotlin/com/subtracks/data/sync/Id3v1Genres.kt

@@ -146,7 +146,7 @@ private val ID3V1_GENRES =
         "Terror",
         "Indie",
         "Britpop",
-        "Negerpunk",
+        "Worldbeat",
         "Polsk Punk",
         "Beat",
         "Christian Gangsta Rap",
@@ -161,7 +161,7 @@ private val ID3V1_GENRES =
         "Anime",
         "Jpop",
         "Synthpop",
-        "Christmas",
+        "Abstract",
         "Art Rock",
         "Baroque",
         "Bhangra",

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

@@ -36,7 +36,7 @@ fun SongInfoDialog(
     localFile: File?,
     streamEncoding: AudioEncoding?,
     onDismiss: () -> Unit,
-    genres: List<String> = emptyList(),
+    genres: List<String>,
 ) {
     val context = LocalContext.current
     var encoding by remember(song.id, localFile) { mutableStateOf<AudioEncoding?>(null) }

app/src/main/kotlin/com/subtracks/ui/home/HomeScreen.kt

@@ -535,13 +535,19 @@ private const val REVEAL_NEAR_FRONT = 1
 internal fun shouldRevealNewFront(
     previousKey: Any?,
     firstKey: Any?,
+    insertedCount: Int,
     firstVisibleItemIndex: Int,
-): Boolean = firstKey != null && previousKey != null && previousKey != firstKey && firstVisibleItemIndex <= REVEAL_NEAR_FRONT
+): Boolean =
+    firstKey != null &&
+        previousKey != null &&
+        previousKey != firstKey &&
+        insertedCount >= 0 &&
+        firstVisibleItemIndex - insertedCount <= REVEAL_NEAR_FRONT
 
 /**
  * Scrolls a row back to the front when a new first item appears while it is already at/near the
- * start. The lazy layout anchors to the previously visible key, so an item that moves to the front
- * after a play lands left of the viewport and is not revealed.
+ * start. The lazy layout anchors to the previously visible key, so a row at the start advances by
+ * the number of prepended items; subtracting that recovers the position the user was actually at.
  */
 @Composable
 internal fun <T> RevealNewFrontItem(
@@ -552,7 +558,11 @@ internal fun <T> RevealNewFrontItem(
     val firstKey = items.firstOrNull()?.let(key)
     var previous by remember { mutableStateOf<Any?>(null) }
     LaunchedEffect(firstKey) {
-        if (shouldRevealNewFront(previous, firstKey, state.firstVisibleItemIndex)) state.animateScrollToItem(0)
+        val oldFront = previous
+        val inserted = if (oldFront != null) items.indexOfFirst { key(it) == oldFront } else -1
+        if (shouldRevealNewFront(oldFront, firstKey, inserted, state.firstVisibleItemIndex)) {
+            state.animateScrollToItem(0)
+        }
         if (firstKey != null) previous = firstKey
     }
 }