V73 FOUR-ELLIPSE CLOVER MODEL

What changed
- Replaces the tilted-petal interpretation with a simpler direct 4-ellipse model.
- The secondary field is now made from:
  * one side ellipse on the main side
  * one side ellipse on the opposite side
  * one end ellipse at the positive strike end
  * one end ellipse at the negative strike end
- The ellipses are shifted slightly outward from the fault body to create a narrow, more acute junction at the corners.

Slider change
- The former Corner pinch angle slider is repurposed as Corner outward gap.
- Increasing this value pushes the ellipses farther outward.

Notes
- Coast override fixes from the previous version are preserved.
