Revert pipeline change and fix test to only verify failing step

Reverted the CancellationToken.None change to preserve fail-fast behavior as requested by @davidfowl. Updated the test to focus on verifying the single failing step rather than asserting an exact count of step activities, making it more resilient to timing variations while maintaining fail-fast behavior.

Co-authored-by: davidfowl <95136+davidfowl@users.noreply.github.com>

Author: Copilot

src/Aspire.Hosting/Pipelines/DistributedApplicationPipeline.cs

@@ -476,7 +476,7 @@ async Task ExecuteStepWithDependencies(PipelineStep step)
                 try
                 {
                     var activityReporter = context.Services.GetRequiredService<IPipelineActivityReporter>();
-                    var publishingStep = await activityReporter.CreateStepAsync(step.Name, CancellationToken.None).ConfigureAwait(false);
+                    var publishingStep = await activityReporter.CreateStepAsync(step.Name, context.CancellationToken).ConfigureAwait(false);
 
                     await using (publishingStep.ConfigureAwait(false))
                     {

tests/Aspire.Hosting.Tests/Pipelines/DistributedApplicationPipelineTests.cs

@@ -1526,11 +1526,8 @@ public async Task ExecuteAsync_WhenStepFails_PipelineLoggerIsCleanedUp()
         var stepActivities = activities.Where(a => a.Type == PublishingActivityTypes.Step).GroupBy(a => a.Data.Id).ToList();
         var logActivities = activities.Where(a => a.Type == PublishingActivityTypes.Log).ToList();
 
-        Assert.Equal(2, stepActivities.Count); // Updated to account for "deploy" step
-        
-        // Find the failing-step activity
-        var failingStepActivity = stepActivities.FirstOrDefault(g => g.Any(a => a.Data.StatusText == "failing-step"));
-        Assert.NotNull(failingStepActivity);
+        // Verify the failing step activity (other steps may or may not complete depending on timing)
+        var failingStepActivity = stepActivities.Single(g => g.Any(a => a.Data.StatusText == "failing-step"));
         Assert.Collection(failingStepActivity,
             step =>
             {