Spike 17 - Dual MC 1x/2x LOD

Loading case table and WebGPU...
FPS: - MC hi verts: - MC low verts: -
Seam strategy: Two MC chunks, same world span, high (62 cells) vs low (31 cells)
Normal continuity: inspect with Wireframe mode / Fly
TX +X verts (debug): -
TX bounds: -
Pipeline mode: Dual MC chunks in Three scene mesh + GPU drawIndirect
Low chunk now has lower triangle density (coarser MC lattice), not quantized SDF values