queue view: disable drag auto-scroll; queue plays next when its anchor is removed

- removing the context track the up-next block sits behind now moves the
  block back behind the preceding track (or to the front when the anchor
  was first), so the queued track plays next instead of the following
  context track.
- disable sh.calvin.reorderable auto-scroll for every run
  (scrollThreshold 0). It keeps scrolling past a run's last valid target
  and can strand the dragged item off-screen; scroll first, then drag.

app/src/test/kotlin/com/subtracks/data/repo/QueueRepositoryTest.kt

@@ -465,6 +465,19 @@ class QueueRepositoryTest {
             assertEquals(listOf("s1", "s4", "s2", "s3"), resolveAll(repository.snapshot()))
         }
 
+    @Test
+    fun removingTheAnchorTrackPutsTheQueueFirst() =
+        runTest {
+            seedLibrary()
+            val snapshot = repository.snapshotAfter(listOf(repository.albumEntry(1, "al1")))
+            repository.addUpNext(snapshot, currentPosition = 0, entry = repository.songEntry(1, "s4"), playNext = false)
+            assertEquals(listOf("s1", "s4", "s2", "s3"), resolveAll(repository.snapshot()))
+
+            repository.removeAt(repository.snapshot(), 0)
+
+            assertEquals(listOf("s4", "s2", "s3"), resolveAll(repository.snapshot()))
+        }
+
     @Test
     fun removingTheLastAnchorTrackKeepsTheQueueResolvable() =
         runTest {

app/src/test/kotlin/com/subtracks/playback/PlaybackControllerTest.kt

@@ -519,7 +519,8 @@ class PlaybackControllerTest {
                 ?.id == "x1"
         }
 
-        assertEquals(1L, runBlocking { queues.cursor() })
+        val snapshot = runBlocking { queues.snapshot() }
+        assertEquals(runBlocking { queues.combinedIndexOf(snapshot, "x1") }, controller.state.value.position)
     }
 
     @Test
@@ -979,7 +980,7 @@ class PlaybackControllerTest {
     }
 
     @Test
-    fun removingThePlayingAnchorTrackPlaysTheModelNextTrack() {
+    fun removingThePlayingAnchorTrackPlaysTheQueuedTrackNext() {
         seedAlbum(4, sourceId = 1)
         seedSong("x1", "al2")
 
@@ -994,11 +995,11 @@ class PlaybackControllerTest {
         runBlocking { controller.removeAt(1) }
         await {
             controller.state.value.item
-                ?.id == "s3"
+                ?.id == "x1"
         }
 
         val snapshot = runBlocking { queues.snapshot() }
-        assertEquals(runBlocking { queues.combinedIndexOf(snapshot, "s3") }, controller.state.value.position)
+        assertEquals(runBlocking { queues.combinedIndexOf(snapshot, "x1") }, controller.state.value.position)
     }
 
     @Test