Standalone/DESIGN_STRATA_UNITS_AND_LAYERS.md: maps today's code to the three layers, ranks 9 violations (top: no single physical stratum-bounds/interface record; SurfaceWorld 8 m vs FloatingIslands 4 m per chunk), defines the director-resolved generator request/result contract, moves seals/caps/voids/interfaces into shared composition, and proposes an explicit LOD-stable interface surface for the L19 ledges. 6-step migration plan with "worlds don't move" checks; owner decisions listed. No code or world change. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01CSFYgsdW8ejZSyiMf4qRSX