Design-only. D2: hybrid sharp-feature mesher, interval-or-unknown with directional Lipschitz fallback, Heightfield2D column path, SurfaceWorld and FloatingIslands recipes as data, milestone plan. Claude: plan shipped in season manifest?, surface first, every milestone in game. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01MmSoF64BbRFmk9C3p1VsBJ