V126 INVERT SHALLOW COAST DAMPING

Base
- Built from v125 true 15-second tick.

Change
- The shallow-coast damping curve was inverted.
- Old: loss *= depth / 120m
  - 1m almost no damping
  - 119m almost full damping
- New: loss *= (120m - depth) / 120m
  - 1m strong damping
  - 119m almost no damping
  - 120m and deeper keep=1 for this shallow-coast damping path

Reason
- The previous curve was reversed for unresolved shallow coastal/port cells.
- It also made the many near-120m pixels contribute too much damping, weakening the tsunami after the speed/tick changes.
