test(streaming): close lifecycle gate after cutover

tests/AcDream.App.Tests/Streaming/LandblockBuildOriginTests.cs

@@ -342,6 +342,58 @@ public sealed class LandblockBuildOriginTests
         Assert.DoesNotContain("_liveCenterY", renderPublisherSource, StringComparison.Ordinal);
     }
 
+    [Fact]
+    public void GameWindowShutdownKeepsStreamerAliveUntilSessionResetConverges()
+    {
+        string source = File.ReadAllText(Path.Combine(
+            FindRepoRoot(),
+            "src",
+            "AcDream.App",
+            "Rendering",
+            "GameWindow.cs"));
+        int sessionStage = source.IndexOf(
+            "new ResourceShutdownStage(\"session lifetime\"",
+            StringComparison.Ordinal);
+        Assert.True(sessionStage >= 0);
+
+        int sessionOperation = source.IndexOf(
+            "new(\"live session\", () =>",
+            sessionStage,
+            StringComparison.Ordinal);
+        Assert.True(sessionOperation > sessionStage);
+
+        int sessionDispose = source.IndexOf(
+            "controller.Dispose()",
+            sessionOperation,
+            StringComparison.Ordinal);
+        Assert.True(sessionDispose > sessionOperation);
+
+        int disposalCompletionBarrier = source.IndexOf(
+            "if (!controller.IsDisposalComplete)",
+            sessionDispose,
+            StringComparison.Ordinal);
+        Assert.True(disposalCompletionBarrier > sessionDispose);
+
+        int sessionReferenceRelease = source.IndexOf(
+            "_liveSessionController = null;",
+            disposalCompletionBarrier,
+            StringComparison.Ordinal);
+        Assert.True(sessionReferenceRelease > disposalCompletionBarrier);
+
+        int dependentStage = source.IndexOf(
+            "new ResourceShutdownStage(\"session dependents\"",
+            sessionReferenceRelease,
+            StringComparison.Ordinal);
+        Assert.True(dependentStage > sessionReferenceRelease);
+
+        int streamerDispose = source.IndexOf(
+            "new(\"streamer\", () => _streamer?.Dispose())",
+            dependentStage,
+            StringComparison.Ordinal);
+
+        Assert.True(streamerDispose > dependentStage);
+    }
+
     private static LandblockBuild EmptyBuild(uint landblockId, LandblockBuildOrigin origin) =>
         new(
             new LoadedLandblock(