[Remote rendering 3.3] Server-authoritative widget state

### 📝 Description of the feature

Sync back the widget state to the server. For toggles (on/off) this can be immediate. For the actual widget interaction, the updated widget state is synced back to the server when the interaction ends (e.g. on mouse-up). When the updated widget state gets synced back to the server, it is applied on the server's vtk pipeline, but a local_view.update() is not triggered, and no round trip is triggered. (this is deferred till phase 6).

Further detail to be added in backlog grooming.

### Acceptance Criteria

- tests clear
- in-visualizer behavior unchanged from main.
- on a refresh, browser state is preserved.

### 💵 Business Value

_No response_

### 🔗 Useful links and references

_No response_