Fixes two SKIP_ONBOARDING bugs and eliminates 10 permanently-skipped integration tests.
- SKIP_ONBOARDING=1 now honoured unconditionally (no longer gated on chat_ready)
- apply_onboarding_setup refuses to write config/env files when SKIP_ONBOARDING is set
- TestMediaEndpointIntegration (6) and TestOnboardingGateIntegration (4): collection-time
skip guards removed; server reachability checked at runtime with fail() not skip()
Tests: 1327 passed, 0 skipped.
Admin merge — self-built PR, Nathan authorized full merge process in session.