replace the seed-flaky block test and cover clearing the block while shuffled

`removingThePlayingTrackWhileShuffledLeavesTheBlockReachable` looped 30
unseeded shuffles and only checked a weak invariant; it is now a single
deterministic case (fixed seed) that asserts the cursor resolves to the
playing track and the queued track still plays next. Add clearing the block
while shuffled, asserting the cursor stays on the playing track.

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

@@ -1701,35 +1701,43 @@ class PlaybackControllerTest {
     fun removingThePlayingTrackWhileShuffledLeavesTheBlockReachable() {
         seedAlbum(6, sourceId = 1)
         seedSong("x1", "al2")
-
-        repeat(30) {
-            if (controller.state.value.shuffle) {
-                controller.toggleShuffle()
-                await { !controller.state.value.shuffle }
-            }
-            runBlocking { controller.clearUpNext() }
-            controller.playAlbum(1, "al1", 2)
-            await {
-                controller.state.value.item
-                    ?.id == "s3" && !controller.state.value.shuffle
-            }
-            controller.addToQueue(1, QueueKind.Song, "x1")
-            await { runBlocking { controller.upcomingItem()?.id } == "x1" }
-
-            controller.toggleShuffle()
-            await { controller.state.value.shuffle }
-            await { runBlocking { controller.upcomingItem()?.id } == "x1" }
-            val current = controller.state.value.position!!
-
-            runBlocking { controller.removeAt(current) }
-
-            val snapshot = runBlocking { queues.snapshot() }
-            val position = controller.state.value.position!!
-            assertTrue(
-                "queued track stranded behind the cursor at $position (block at ${snapshot.anchorPlay})",
-                position <= snapshot.anchorPlay || snapshot.isUpNext(position),
-            )
+        runBlocking {
+            queues.replace(listOf(queues.albumEntry(1, "al1")))
+            queues.setShuffle(2024L)
+            queues.setCursor(0)
         }
+        controller.connect()
+        await { controller.state.value.item != null && controller.state.value.shuffle }
+        controller.addToQueue(1, QueueKind.Song, "x1")
+        await { runBlocking { controller.upcomingItem()?.id } == "x1" }
+
+        val current = controller.state.value.position!!
+        runBlocking { controller.removeAt(current) }
+
+        val after = runBlocking { queues.snapshot() }
+        assertTrue(after.shuffled)
+        assertEquals(
+            controller.state.value.item
+                ?.id,
+            runBlocking { queues.itemAt(after, controller.state.value.position!!)?.song?.id },
+        )
+        await { runBlocking { controller.upcomingItem()?.id } == "x1" }
+    }
+
+    @Test
+    fun clearingTheBlockWhileShuffledKeepsTheCursorOnThePlayingTrack() {
+        seedShuffledQueue(seed = 7L)
+        val currentId =
+            controller.state.value.item!!
+                .id
+        controller.addToQueue(1, QueueKind.Song, "s1")
+        await { runBlocking { controller.upcomingItem()?.id } == "s1" }
+
+        controller.clearUpNext()
+
+        await { runBlocking { queues.snapshot().upNext }.isEmpty() }
+        val after = runBlocking { queues.snapshot() }
+        assertEquals(currentId, runBlocking { queues.itemAt(after, controller.state.value.position!!)?.song?.id })
     }
 
     @Test