Fix flaky EventDrivenFlowCompletesSuccessfully tests by using BusyWaitUntil

Replace fixed Task.Delay with BusyWaitUntil polling for Suspended status,
matching the pattern already used in ParamlessFlowsTests.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: stidsborg

Cleipnir.Tests/Flows/FlowsWithResultTests.cs

@@ -109,10 +109,9 @@ public async Task EventDrivenFlowCompletesSuccessfully()
         var flows = new MessageDrivenFuncFlows(flowsContainer);
         await flows.Schedule("someInstanceId", "someParameter");
 
-        await Task.Delay(10);
         var controlPanel = await flows.ControlPanel(instanceId: "someInstanceId");
         controlPanel.ShouldNotBeNull();
-        controlPanel.Status.ShouldBe(Status.Suspended);
+        await controlPanel.BusyWaitUntil(c => c.Status == Status.Suspended);
 
         var messageWriter = flows.MessageWriter("someInstanceId");
         await messageWriter.AppendMessage(new IntWrapper(2));

Cleipnir.Tests/Flows/UnitFlowsTests.cs

@@ -70,10 +70,9 @@ public async Task EventDrivenFlowCompletesSuccessfully()
 
         await flows.Schedule("someInstanceId", "someParameter");
 
-        await Task.Delay(10);
         var controlPanel = await flows.ControlPanel(instanceId: "someInstanceId");
         controlPanel.ShouldNotBeNull();
-        controlPanel.Status.ShouldBe(Status.Suspended);
+        await controlPanel.BusyWaitUntil(c => c.Status == Status.Suspended);
 
         var eventSourceWriter = flows.MessageWriter("someInstanceId");
         await eventSourceWriter.AppendMessage(new IntWrapper(2));