Here is the complete HTML page with an embedded 3D WebGL scene built using Three.js. It precisely follows all the dimensions, geometry, and placement details you provided in the description.
Save this code into an `index.html` file and open it in any modern web browser to interact with the 3D seastead design.
```html
Seastead Design - 3D Visualization
Seastead Concept
Interactive View: Left-click & drag to rotate. Right-click to pan. Scroll to zoom.