fix up-next drag and previous behaviour

- set lastPosition before seeking in jumpTo. With Dispatchers.Main
  .immediate the media transition runs synchronously inside the seek, so
  onPositionChanged saw the old position as an auto-advance and consumed
  the track you were leaving; previous from a queued track removed it and
  played the next one.
- give the up-next and context sections their own reorderable states. The
  library only targets items whose key is in that state's reorderableKeys,
  so a drag can no longer target a row in the other section: no more
  fighting the section boundary when dragging to the top and no no-op drop
  below the block.
- disable context reordering while shuffled via ReorderableItem(enabled).

app/src/main/kotlin/com/subtracks/playback/PlaybackController.kt

@@ -870,12 +870,12 @@ class PlaybackController(
                     endedHandled = false
                     return@withLock
                 }
+                lastPosition = dest
                 shiftWindowLocked(dest)
                 player.ensurePrepared()
                 player.seekToIndex((dest - windowStart).toInt())
                 if (wasEnded) player.play()
                 endedHandled = false
-                lastPosition = dest
                 refresh(dest)
             }
         }

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

@@ -317,7 +317,11 @@ fun QueueScreen(
     var dragId by remember { mutableStateOf<Long?>(null) }
     var dragFrom by remember { mutableStateOf<Long?>(null) }
 
-    val reorderState =
+    val upNextReorder =
+        rememberReorderableLazyListState(listState) { from, to ->
+            onReorder(from.index, to.index)
+        }
+    val contextReorder =
         rememberReorderableLazyListState(listState) { from, to ->
             onReorder(from.index, to.index)
         }
@@ -378,10 +382,11 @@ fun QueueScreen(
                         if (index == 0 || rows[index - 1].upNext != row.upNext) {
                             QueueSectionHeader(if (row.upNext) "Up next" else contextTitle ?: "Next up")
                         }
-                        val draggable = row.upNext || !shuffle
+                        val enabled = row.upNext || !shuffle
                         ReorderableItem(
-                            state = reorderState,
+                            state = if (row.upNext) upNextReorder else contextReorder,
                             key = row.id,
+                            enabled = enabled,
                             animateItemModifier =
                                 Modifier.animateItem(
                                     fadeInSpec = tween(150),
@@ -395,7 +400,7 @@ fun QueueScreen(
                                 floating = isDragging,
                                 coverArt = coverArt,
                                 dragHandle =
-                                    if (!draggable) {
+                                    if (!enabled) {
                                         null
                                     } else {
                                         Modifier.draggableHandle(