ValidateOrder and EnrichOrder call YieldOutputAsync with string messages,
but only their TOutput (OrderDetails) was in the allowed yield types.
This caused TargetInvocationException in the WorkflowSharedState sample
validation integration test.
- Add UTF-8 BOM to 20 .cs files across DurableTask, AzureFunctions,
unit tests, and workflow samples
- Remove unnecessary using directive in 07_SubWorkflows/Executors.cs
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>