1. Protect placed presets and preset walls from being wiped in stampThemedRoads:
check placedRects in paintRoadTile, ensuring preset walls are never cleared.
2. Protect preset floors and walls in stampAct3KurastCauseway so artist DS1
tiles are not overwritten by procedural causeway passes; wire specialPlacedRects.
3. Protect placed preset walls and floors in synthesizeBridgePlanks in Act 3 jungles,
recording placedRects for all jungle pieces.
4. Add unit tests for Causeway preset preservation and road preset wall preservation.
TAG=agy
CONV=2a1934de-30ef-464e-b3f3-fcbcdbbc49f1
troytt