GROUND_COVERED_BIT

Bit 7 of the stencil byte = "covered by a ground-group drawable" (e.g. 3D-Tile mesh). Written by ground-group draws that participate in terrain composition, tested by BasicDrawableTerrain.drawTriangles so terrain skips pixels claimed by mesh content. Bits 0..6 stay free for subsystem-specific use (e.g. Cesium skip-LoD subtree ids).