perf(render): bound animation and alpha scratch residency

Complete Slice D3 by replacing the unbounded animation dictionary with a concurrent byte/count LRU and by putting the three retail alpha scratch owners behind one typed aggregate budget. Preserve immediate growth and draw order while reclaiming one-frame density spikes after sustained under-use. Close stale bounds-cache issue evidence without inventing a cache.

tests/AcDream.App.Tests/Rendering/Residency/ResidencyManagerTests.cs

@@ -7,6 +7,20 @@ public sealed class ResidencyManagerTests
     private sealed class MeshAsset;
     private sealed class TextureAsset;
 
+    [Fact]
+    public void ScratchBytesAreCommittedCpuResidence()
+    {
+        var charges = new ResidencyCharges(
+            LogicalBytes: 1,
+            CpuPreparedBytes: 2,
+            DecodedBytes: 3,
+            ScratchBytes: 4,
+            StagingBytes: 5);
+
+        Assert.Equal(15, charges.CommittedCpuBytes);
+        charges.Validate();
+    }
+
     [Fact]
     public void HandlesAndOwnersReserveZeroAsInvalid()
     {