fix(rendering): normalize empty dispatcher evidence

tests/AcDream.App.Tests/Rendering/Wb/InstanceGroupClearTests.cs

@@ -1,4 +1,5 @@
 using System.Numerics;
+using AcDream.App.Rendering.Scene;
 using AcDream.App.Rendering.Wb;
 using AcDream.Core.Meshing;
 using Xunit;
@@ -138,6 +139,36 @@ public class InstanceGroupClearTests
             reversedSubmission.TransparentSetDigest);
     }
 
+    [Fact]
+    public void DispatcherFingerprint_ZeroVisibleInstancesIgnoresStaleGroupStorage()
+    {
+        WbDrawDispatcher.InstanceGroup stale = MakeCompleteGroup(
+            textureHandle: 0xAA,
+            submissionOrder: 0);
+        var scratch = new List<WbDrawDispatcher.AlphaFingerprint>();
+
+        CurrentRenderDispatcherSubmission expected =
+            WbDrawDispatcher.CreateDispatcherSubmission(
+                visibleInstanceCount: 0,
+                immediateInstanceCount: 0,
+                deferTransparent: false,
+                opaque: [],
+                transparent: [],
+                cameraWorldPosition: Vector3.Zero,
+                alphaScratch: scratch);
+        CurrentRenderDispatcherSubmission actual =
+            WbDrawDispatcher.CreateDispatcherSubmission(
+                visibleInstanceCount: 0,
+                immediateInstanceCount: 0,
+                deferTransparent: false,
+                opaque: [stale],
+                transparent: [stale],
+                cameraWorldPosition: Vector3.Zero,
+                alphaScratch: scratch);
+
+        Assert.Equal(expected, actual);
+    }
+
     [Fact]
     public void CachedGroupHandle_RequiresLiveMatchingRegistration()
     {