Revert "Merge pull request #251 from mlemanczyk/codex/refactor-prime-checking-on-gpu-n5t2pm"

This reverts commit 936ce239db, reversing
changes made to e14b77e504.

PerfectNumbers.Core.Tests/Gpu/PrimeTesterGpuTests.cs

@@ -10,6 +10,7 @@ public class PrimeTesterGpuTests
     [Fact]
     public void IsPrimeGpu_accepts_known_primes()
     {
+        GpuContextPool.ForceCpu = false;
         try
         {
             var tester = new PrimeTester();
@@ -21,6 +22,7 @@ public class PrimeTesterGpuTests
         }
         finally
         {
+            GpuContextPool.ForceCpu = false;
             GpuContextPool.DisposeAll();
         }
     }
@@ -28,6 +30,7 @@ public class PrimeTesterGpuTests
     [Fact]
     public void IsPrimeGpu_rejects_composites()
     {
+        GpuContextPool.ForceCpu = false;
         try
         {
             var tester = new PrimeTester();
@@ -39,6 +42,7 @@ public class PrimeTesterGpuTests
         }
         finally
         {
+            GpuContextPool.ForceCpu = false;
             GpuContextPool.DisposeAll();
         }
     }