Guard residue GPU scanning with execution lock

PerfectNumbers.Core/Gpu/MersenneNumberResidueGpuTester.cs

@@ -17,11 +17,16 @@ public class MersenneNumberResidueGpuTester(bool useGpuOrder)
     public void Scan(ulong exponent, UInt128 twoP, bool lastIsSeven, UInt128 maxK, ref bool isPrime)
     {
         var gpuLease = GpuKernelPool.GetKernel(_useGpuOrder);
+        var execution = gpuLease.EnterExecutionScope();
+        try
+        {
             var accelerator = gpuLease.Accelerator;
             var stream = gpuLease.Stream;
+
             // Ensure device has small cycles and primes tables for in-kernel lookup
             var smallCyclesView = GpuKernelPool.EnsureSmallCyclesOnDevice(accelerator);
             ResiduePrimeViews primeViews = GpuKernelPool.EnsureSmallPrimesOnDevice(accelerator);
+
             int batchSize = GpuConstants.ScanBatchSize;
             UInt128 kStart = 1UL;
             UInt128 limit = maxK + UInt128.One;
@@ -41,13 +46,15 @@ public class MersenneNumberResidueGpuTester(bool useGpuOrder)
             // testers such as the order kernels.
             orderBuffer.MemSetToZero();
             ulong[] orderArray = ArrayPool<ulong>.Shared.Rent(batchSize);
-        UInt128 batchSize128 = (UInt128)batchSize;
-        UInt128 fullBatchStep = twoP * batchSize128;
-        UInt128 q = twoP * kStart + UInt128.One;
-        // TODO: Replace the direct UInt128 multiply/add updates below with the residue-cycle stepping helper so that q advances reuse cached cycle increments rather than recomputing twoP multiples on every iteration.
 
             try
             {
+                UInt128 batchSize128 = (UInt128)batchSize;
+                UInt128 fullBatchStep = twoP * batchSize128;
+                UInt128 q = twoP * kStart + UInt128.One;
+                // TODO: Replace the direct UInt128 multiply/add updates below with the residue-cycle stepping helper so that q advances
+                // reuse cached cycle increments rather than recomputing twoP multiples on every iteration.
+
                 while (kStart < limit && Volatile.Read(ref isPrime))
                 {
                     UInt128 remaining = limit - kStart;
@@ -101,8 +108,13 @@ public class MersenneNumberResidueGpuTester(bool useGpuOrder)
             }
             finally
             {
-            ArrayPool<ulong>.Shared.Return(orderArray);
+                ArrayPool<ulong>.Shared.Return(orderArray, clearArray: false);
                 orderBuffer.Dispose();
+            }
+        }
+        finally
+        {
+            execution.Dispose();
             gpuLease.Dispose();
         }
     }