fix(engine): discard cancelled pipeline results from uncooperative engines

OpenNest.Engine.Tests/Jobs/NestPipelineTests.cs

@@ -101,6 +101,21 @@ public class NestPipelineTests
         Assert.Contains("Default", error.Message);
     }
 
+    [Fact]
+    public void CancellationDuringSolveDiscardsEvenAnEngineThatReturnsNormally()
+    {
+        using var cts = new CancellationTokenSource();
+        var engine = new StubEngine(job =>
+        {
+            cts.Cancel();
+            return OnePlate(job, new NestJobPlacement(job.Parts[0].Id, 0, 1, 1, 0));
+        });
+
+        Assert.ThrowsAny<OperationCanceledException>(() =>
+            NestPipeline.Run(engine, "IgnoresStop", Request("IgnoresStop", Item("bracket", 1)), null, cts.Token)
+        );
+    }
+
     [Fact]
     public void CancellationPropagatesWithoutAResult()
     {

OpenNest.Engine/Jobs/NestPipeline.cs

@@ -115,6 +115,7 @@ public static class NestPipeline
             engine.Solve(job, progress, token)
             ?? throw new InvalidOperationException($"Engine '{engineName}' returned no result.");
         var solveTime = clock.Elapsed;
+        token.ThrowIfCancellationRequested();
 
         clock.Restart();
         var violations = Validate(job, raw, drawingsByPartId);
@@ -128,6 +129,7 @@ public static class NestPipeline
             ))
             .ToList();
 
+        token.ThrowIfCancellationRequested();
         return new NestPipelineResult(
             engineName,
             job,