Here is the full HTML file with a complete 3D WebGL scene of the 1:4 scale prototype seastead using Three.js.
You can save this code as an `.html` file (for example, `seastead.html`) and open it in any modern web browser to view, rotate, and zoom the 3D model.
```html
1:4 Prototype Seastead Drone
Seastead Drone Prototype (1:4 Scale)
Left/Click to Rotate | Scroll to Zoom | Right/Click to Pan
```