Embed GPU scratch buffers in context leases

PerfectNumbers.Core/HeuristicPrimeTester.cs

@@ -270,13 +270,12 @@ public sealed class HeuristicPrimeTester
         var gpu = PrimeTester.PrimeTesterGpuContextPool.Rent(batchCapacity, 1);
         var accelerator = gpu.Accelerator;
         var state = gpu.State;
-        var scratch = gpu.Scratch;
 
         bool compositeDetected = false;
         int count = 0;
 
-        var inputView = scratch.Input.View;
-        var outputView = scratch.Output.View;
+        var inputView = gpu.Input.View;
+        var outputView = gpu.Output.View;
 
         bool ProcessBatch(int length)
         {