bounded_probe_run now spawns through local_runtime.processes.spawn_server on
Windows (CREATE_SUSPENDED + AssignProcessToJobObject on the real handle), which
a fake Popen cannot satisfy, so the probe fell to its fail-open "" and the
contract assertions never ran (windows-only job on 0eae148f0d). Fake the
container instead; the kwargs the probe hands it are the contract under test.