fix: snapshot RN synthetic events and prevent channel echo (#856)

- Add patchChannelForRN to snapshot synthetic event args before React
  recycles them, avoiding stale event pool errors in the actions panel
- Limit channel serialization depth to prevent circular reference crashes
- Stop WebSocket server from echoing messages back to the sender
- Fix polyfill.ts import to use react-native instead of react-native-web
- Move setImmediate workaround from Start.tsx to polyfill.ts