WAM broker fails with window_handle_required on 3rd auth call in console apps

[shyamsridhar123]

I wrote a detailed report covering the root cause (3 auth calls, pinned account ID breaks WAM on call 3), repro steps, environment info, all the workarounds we tried, and a suggested fix (fall back to OperatingSystemAccount sentinel when the pinned account gets AccountNotFound).

[juhisaha-p1]

Seems like this is related to #64