Runtime dynamic tests (AddDynamicTest) discard the Task of async test methods, hiding failures #7249

What happens

A dynamic test added at run time with TestContext.AddDynamicTest whose method returns Task passes even when the method throws after its first await. For example, a failing await Assert.That(...) is never reported.

TestRegistry.CreateRuntimeTestInvoker (src/TUnit.Engine/Services/TestRegistry.cs, around line 338) compiles DynamicTest<T>.TestMethod. That is an Expression<Action<T>>, so the compiled delegate is an Action<T>. invokeMethod.Invoke(...) returns null, and the invokeResult is Task task branch never runs, so the method's Task is dropped.

The [DynamicTestBuilder] path (ReflectionTestDataCollector.CreateDynamicTestInvoker) is not affected: it extracts the MethodInfo and awaits the returned task.

How to reproduce

public class Consumer
{
    public async Task Fails()
    {
        await Task.Yield();
        throw new Exception("should fail");
    }
}

public class Builder
{
    [Test]
    public async Task Adds()
    {
        await TestContext.Current!.AddDynamicTest(new DynamicTest<Consumer>
        {
            TestMethod = c => c.Fails(),
            Attributes = []
        });
    }
}

The dynamic Fails test is reported as passed. I found this while writing the regression test for #7204 (PR #7248): an async Task assertion on a disposed fixture passed until I made the method synchronous.

Expected

The dynamic test fails. One option: when the lambda body is a method call that returns Task or ValueTask, invoke it through its MethodInfo (as CreateDynamicTestInvoker does), or compile the body into a Func<T, object?> so the result can be awaited.