feat: harden isolated Tornado test workflow

tests/MBN_STOCK_WEBVIEW.Playout.Tests/DryRunPlayoutEngineTests.cs

@@ -99,6 +99,31 @@ public sealed class DryRunPlayoutEngineTests
         Assert.Null(engine.Status.OnAirSceneName);
     }
 
+    [Fact]
+    public async Task DryRun_NextAfterPrepareButBeforeTakeInIsRejected()
+    {
+        await using var engine = CreateEngine(PlayoutMode.DryRun);
+        var idleNext = await engine.NextAsync(
+            Cue("next-scene"),
+            CancellationToken.None);
+
+        Assert.Equal(PlayoutResultCode.Rejected, idleNext.Code);
+        Assert.Null(engine.Status.PreparedSceneName);
+        Assert.Null(engine.Status.OnAirSceneName);
+
+        Assert.True((await engine.PrepareAsync(
+            Cue("first-scene"),
+            CancellationToken.None)).IsSuccess);
+
+        var next = await engine.NextAsync(
+            Cue("next-scene"),
+            CancellationToken.None);
+
+        Assert.Equal(PlayoutResultCode.Rejected, next.Code);
+        Assert.Equal("first-scene", engine.Status.PreparedSceneName);
+        Assert.Null(engine.Status.OnAirSceneName);
+    }
+
     [Fact]
     public async Task CancelledDryRunCommand_DoesNotChangeStatus()
     {