test(setup): assert stalled preflight outcome

[Sykezzz]

Summary

• verify that a stalled signer inspection fails closed with timeout exit code 2
• keep a 30-second outer harness kill switch for loaded hosted runners
• leave production inspection timeout, process-tree cleanup bound, trust checks, and Setup behavior unchanged

Evidence

• hosted Python 3.10 startup exceeded both 9.5s and 15s before the helper's internal timers could provide a stable external wall-clock signal
• tests/test_build_profiles.py: 11 passed