V81 PRESET LOAD: REBUILD HEIGHT FROM SLIP + DEPTH

Base
- Starts from V80.
- Secondary deformation remains disabled.
- Coast fix / Shimonoseki 10% choke / coast absorb fix / V80 depth-efficiency retune are preserved.

What changed
- When loading a preset SOURCE row with slip_m present, slip_m is now treated as the authoritative finite-fault value.
- The source height_m is rebuilt from slip_m, per-source dip_deg, per-source depth_km, current strike-slip mix, and the current depth-efficiency curves.
- This means old presets automatically update their injected water height when the depth-efficiency model changes.

Skipped rows
- Auto-secondary rows with patch_id < 0 are not rebuilt.
- Rows without usable slip keep their stored height.

Status
- After loading, the status line reports how many source points were rebuilt from slip+depth.
