recording_state_transition_invalid· reason_code· applies to event_envelopeAn `ak.call.state` event requested a `recording_transition` or `transcript_transition` not listed in the per-capture controlled state machine (e.g. transitioning out of terminal `ready` / `failed`, `stopped → failed`, or attempting to enter a capturing state without a new `ak.call.recording.start`). The reducer MUST `failed_precondition`. The same code covers both orthogonal capture dimensions. See zh/crypto-media/call-state.md §4.2.