refactor(render): extract world scene frame owner

Move fallback and PView world drawing, shared alpha, particles, visibility, selection, and diagnostics behind focused frame owners. Make exceptional frames failure-atomic by restoring the shared GL baseline and preserving primary alpha failures through cleanup.

Co-authored-by: Codex <codex@openai.com>

tests/AcDream.App.Tests/Rendering/RetailAlphaQueueTests.cs

@@ -179,6 +179,76 @@ public sealed class RetailAlphaQueueTests
             log);
     }
 
+    [Fact]
+    public void AbortFrame_DiscardsPayloadAndAllowsTheNextFrameToRender()
+    {
+        var log = new List<string>();
+        var source = new RecordingSource("alpha", log);
+        var queue = new RetailAlphaQueue();
+
+        queue.BeginFrame();
+        queue.Submit(source, 1, 12f);
+        queue.AbortFrame();
+
+        Assert.False(queue.IsCollecting);
+        Assert.Equal(0, queue.PendingCount);
+        Assert.Empty(log);
+        Assert.Equal(1, source.ResetCount);
+
+        queue.BeginFrame();
+        queue.Submit(source, 2, 12f);
+        queue.EndFrame();
+
+        Assert.Equal(["alpha:2"], log);
+        Assert.Equal(2, source.ResetCount);
+    }
+
+    [Fact]
+    public void EndFrame_DrawAndResetFailuresPreserveThePrimaryFailureAndClearTheFrame()
+    {
+        var drawSource = new FailureSource("draw failed", "first reset failed");
+        var secondSource = new FailureSource(null, null);
+        var queue = new RetailAlphaQueue();
+
+        queue.BeginFrame();
+        queue.Submit(drawSource, 1, 20f);
+        queue.Submit(secondSource, 2, 10f);
+
+        AggregateException failure = Assert.Throws<AggregateException>(queue.EndFrame);
+
+        Assert.Collection(
+            failure.InnerExceptions,
+            error => Assert.Equal("draw failed", error.Message),
+            error => Assert.Equal("first reset failed", error.Message));
+        Assert.Equal(1, drawSource.ResetCount);
+        Assert.Equal(1, secondSource.ResetCount);
+        Assert.Equal(0, queue.PendingCount);
+        Assert.False(queue.IsCollecting);
+    }
+
+    [Fact]
+    public void EndFrame_MultipleResetFailuresAttemptEverySourceAndClearTheFrame()
+    {
+        var first = new FailureSource(null, "first reset failed");
+        var second = new FailureSource(null, "second reset failed");
+        var queue = new RetailAlphaQueue();
+
+        queue.BeginFrame();
+        queue.Submit(first, 1, 20f);
+        queue.Submit(second, 2, 10f);
+
+        AggregateException failure = Assert.Throws<AggregateException>(queue.EndFrame);
+
+        Assert.Collection(
+            failure.InnerExceptions,
+            error => Assert.Equal("first reset failed", error.Message),
+            error => Assert.Equal("second reset failed", error.Message));
+        Assert.Equal(1, first.ResetCount);
+        Assert.Equal(1, second.ResetCount);
+        Assert.Equal(0, queue.PendingCount);
+        Assert.False(queue.IsCollecting);
+    }
+
     [Fact]
     public void ComputeViewerDistance_UsesTransformedGfxSortCenter()
     {
@@ -224,4 +294,28 @@ public sealed class RetailAlphaQueueTests
 
         public void ResetAlphaSubmissions() => ResetCount++;
     }
+
+    private sealed class FailureSource(
+        string? drawFailure,
+        string? resetFailure) : IRetailAlphaDrawSource
+    {
+        public int ResetCount { get; private set; }
+
+        public void PrepareAlphaDraws(ReadOnlySpan<int> tokens)
+        {
+        }
+
+        public void DrawPreparedAlphaBatch(int firstPreparedDraw, int drawCount)
+        {
+            if (drawFailure is not null)
+                throw new InvalidOperationException(drawFailure);
+        }
+
+        public void ResetAlphaSubmissions()
+        {
+            ResetCount++;
+            if (resetFailure is not null)
+                throw new InvalidOperationException(resetFailure);
+        }
+    }
 }