Function isFlowEvent

isFlowEvent<T>(event: T): event is Exclude<T, { pipelineId: string }>
Discriminator for the union payload types on CombinedRecorder's shared methods (onError, onPause, onResume). Returns true if the event was emitted from the control-flow channel (FlowRecorder).

How it discriminates
1. Explicit channel field first (backlog B3): every engine-dispatched shared-method event is stamped channel: 'flow' (control-flow) or channel: 'scope' (data-flow) at construction. This is the positive, schema-robust signal — it survives wrappers that add/strip fields.
2. Legacy fallback for unstamped events (consumer-fabricated tests, persisted traces from <9.2): scope-channel events extend RecorderContext, which carries pipelineId; flow-channel events do not. The flow variant is detected by the ABSENCE of pipelineId — schema-stable as long as scope events continue to extend RecorderContext, but fragile against field-stripping wrappers, which is why the explicit discriminant now exists.
Type Parameters
- T
Parameters
- event: T
Returns event is Exclude<T, { pipelineId: string }>
Example
```
onError: (e) => {
  if (isFlowEvent(e)) {
    // Narrowed to FlowErrorEvent: has stageName, message, structuredError
  } else {
    // Narrowed to ErrorEvent: has error, operation, key?
  }
}
```
- Defined in lib/recorder/CombinedRecorder.ts:182