test: stabilize single-flight concurrency fixtures

allstarr.Tests/Playlists/PlaylistOrchestrationIntegrationTests.cs

@@ -802,7 +802,7 @@ public sealed class PlaylistOrchestrationIntegrationTests(ITestOutputHelper outp
                 It.IsAny<ProtocolExecutionContext>(), "Concurrent external", 60))
             .Returns(async () =>
             {
-                if (Interlocked.Increment(ref entered) == 8)
+                if (Interlocked.Increment(ref entered) == snapshotIds.Length)
                     release.SetResult();
                 await release.Task;
                 return

allstarr.Tests/Providers/MultiProviderMetadataServiceTests.cs

@@ -52,19 +52,25 @@ public sealed class MultiProviderMetadataServiceTests
     [Fact]
     public async Task Provider_deadline_is_linked_to_the_underlying_operation()
     {
-        var cancelled = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
+        var cancellationObserved = false;
 
         await Assert.ThrowsAsync<TimeoutException>(() =>
             MultiProviderMetadataService.RunTimedAsync(
                 async token =>
                 {
-                    using var registration = token.Register(cancelled.SetResult);
-                    await Task.Delay(Timeout.InfiniteTimeSpan, token);
-                    return 1;
+                    try
+                    {
+                        await Task.Delay(Timeout.InfiniteTimeSpan, token);
+                        return 1;
+                    }
+                    finally
+                    {
+                        cancellationObserved = token.IsCancellationRequested;
+                    }
                 },
                 TimeSpan.FromMilliseconds(25),
                 CancellationToken.None));
 
-        await cancelled.Task.WaitAsync(TimeSpan.FromSeconds(5));
+        Assert.True(cancellationObserved);
     }
 }