V54 BRUSH-MASK SECONDARY DEFORMATION

What changed
- Point-click finite-fault patches are first rebuilt into a continuous fault mask, instead of treating them as sparse sample points or one global envelope.
- Each direct rupture patch now contributes its own local rounded footprint to the mask.
- Small gaps between adjacent stamped patches are filled, so the reconstructed mask behaves more like the older brush-painted mode.
- The auto secondary deformation is then generated as a soft halo around that reconstructed mask boundary.

Why
- The older brush mode looked correct because it already had a filled area.
- The newer mode stores many clicked patch pieces; if the secondary field is generated directly from those points or from a coarse envelope, it tends to become a stripe / blob shape.
- Reconstructing the filled fault footprint first should make the result closer to the manual brush result.

Operational notes
- Press G to regenerate the automatic secondary deformation after editing the finite-fault model.
- If the preferred subsidence side looks flipped, use D and regenerate again.

Implementation note
- This is still an empirical secondary-field generator, not a full Okada solution.
- The main purpose of V54 is shape recovery: point-click faults should behave more like brush-painted faults.
