Quiet caller audio (sub-VAD-threshold) so the local VAD stays silent; the MockRealtimeBrain advisory schedule emits speech_started after 2 appends and the kill flows through slice-3's real advisory plumbing: mock -> translator -> tap protocol -> tap_client -> advisory_tx -> Reflex. Proves the ASR-VAD backstop path (spec §3.1, §6; done-criteria #8). Signed-off-by: Aaron D. Lee <himself@adlee.work>