call_state_terminal· reason_code· applies to event_envelopeAn `ak.call.state` event attempted to transition `state_transition.from` out of a terminal value (`ended` / `missed` / `failed` / `cancelled`). Call lifecycle is monotonic; the reducer MUST `failed_precondition`. Capture lifecycles use orthogonal per-segment transition typed results. See zh/crypto-media/call-state.md §4.2.