"data" events are duplicated

When a device publishes data items, the `data` event is received twice for each publication, with repeated information.

e.g.
```{from: '6e5a681b2ae7be40', payload: {sensorId: 2, value: 24}}```
```{from: '6e5a681b2ae7be40', payload: {sensorId: 2, value: 24}}```
```{from: '6e5a681b2ae7be40', payload: {sensorId: 1, value: true}}```
```{from: '6e5a681b2ae7be40', payload: {sensorId: 1, value: true}}```

The issue identifies duplicated data events in the WebSocket protocol adapter but names no files, tests, or entry points. Start by reproducing a device publication and tracing where data events are emitted; done means each published item produces one event with no repeated information, with a regression test if the repository has an established test location.

Written by the indexing model from the issue text.