V82 GLOBAL 6-HOUR DECAY RETUNE

Base
- Starts from V81.

Change
- GLOBAL_HEIGHT_DECAY_KEEP_6H changed from 0.955 to 0.850.
- This means the global wave-height field keeps 85% amplitude per 6 simulated hours.
- Equivalent attenuation: 15% amplitude loss per 6h.

Preserved from recent versions
- Auto secondary deformation disabled.
- Coast override correction with land at 564,426.
- Shimonoseki / Kanmon cell 332,225 damped to about 10% transmission.
- Coast absorb fix.
- Depth-efficiency retune and preset load recalculation from slip/depth.
