wip(unreal): round 4 -- strate-type coverage matrix; SurfaceWorld via exact legacy bridge

Luna, integration round 4 (owner requirement: Core must know every strate type).
Coverage, Core vs legacy owner field (one probe per type, 686,000 LOD0 samples):
  TunnelNetwork approximate (2.17% signs differ); FlatPlain / CrystalChamber native slab
  fields missing (generic cave, 1.28%); Maze missing (13.3%); VerticalShafts missing (no
  shaft surface); FloatingIslands missing (95.8%); Underwater approximate + no water.
  SurfaceWorld: exact density (0 sign changes, LOD0-3 hashes match) through the copied
  legacy evaluator -- but at legacy cost: full view 23.1 s vs legacy 23.9 s (Core caves
  without surface 0.785 s).
  Passages: SlopedTunnel/VerticalShaft/Spiral pass walkability; Cascading (365/1,495) and
  Worm (109/1,490) FAIL. Transitions approximate (1.2-1.3%).
BuildHost UBT + actor validation pass (SurfaceWorld layout: 2,553 visual keys, 448 LOD
transitions, biome query). Small owner/Core capture pairs in core_strate_coverage/.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MmSoF64BbRFmk9C3p1VsBJ

CODEMAP.md

@@ -820,7 +820,7 @@ second density path.
 | `VoxelForgeWormBlockSkipTest.cpp` | `VoxelForge.Determinism.WormBlockSkipSoundness` | Soundness and coverage of the worker-local worm N1 block proof (`voxel.WormBlockSkip`). |
 | `VoxelForgePlayerFitWindow.h` | — | Shared measurement-window policy for player-fit diagnostics (test/editor side only). |
 
-### 3.13 Core runtime integration (rounds 2–3)
+### 3.13 Core runtime integration (rounds 2–4)
 The public Core API is linked as the `VoxelForgeCore` runtime module, with canonical implementation
 sources still under `Standalone/`. UBT validates the 18-row manifest and its shims; BuildHost linked
 the module and passed `CheckCoreSymbols.ps1` against the actual shim objects. See
@@ -850,6 +850,23 @@ is the narrow switch-off baseline; it passes, but does not instantiate an actor
 See the report for that limitation, the changed world hashes, classification evidence, and owner-editor
 instructions. The Core route is opt-in; the legacy path remains the default.
 
+Round 4 adds a temporary SurfaceWorld density bridge in
+[ShapeWorldInternal.h](Standalone/Core/src/ShapeWorldInternal.h). SurfaceWorld samples, including
+biome resolution and terrain operations, route through the copied owner evaluator at full resolution;
+the Core edit layer is applied afterward. Surface density hashes match the owner field across the
+tested LOD0–LOD3 tiles, and the BuildHost actor layout identifies Biome_Surface_Plain at the surface
+travel point. The CPU bridge costs approximately the legacy field route: 23.085 s wall / 180.562
+worker-seconds for the matched 1,294-tile CPU view.
+
+[OwnerWorldLoader.h](Standalone/Source/OwnerWorldLoader.h) now reads SlabParams, MazeParams,
+VerticalShaftParams, and FloatingIslandParams. The shape-world evaluator still lacks their native
+terrain fields: FlatPlain, CrystalChamber, Maze, VerticalShafts, FloatingIslands, and water
+presentation remain missing or approximate. Passage type/style chains are extracted from manager
+control points, but Worm and Cascading currently fail the centerline walkability audit. Gradient,
+Hard, and Interleaved transitions produce the same Core probe hash and are not faithfully represented.
+See the [round-4 coverage table and small matched captures](Standalone/UNREAL_INTEGRATION_REPORT.md)
+and [probe artifacts](Standalone/Research/OwnerShapeWorld/core_strate_coverage/).
+
 ## 4. The density pipeline (most-edited hot path)
 
 ### 4.1 `GetDensityWithParams` (TunnelNetwork) — VoxelGenerator.cpp:3749