wip(assembler): M2 round 3 -- opt-in hybrid sharp mesher (WorldAssemblerHybridV1) in the Unreal Core route

Default MarchingCubesV1 unchanged (W1/W8/W16 = round-6 hashes). Hybrid DC only in LOD0 interior cells
with tagged features; tile-border cells and LOD1+ stay MC. BuildHost: fixtures repeat exactly, cooked
collision bounds = render bounds, same-LOD borders pass, sampled SurfaceWorld cliff bit-identical to MC.
Open: tagged tiles cost 5.7-6.7x MC; corner-top field contact error 20 cm; 5 MC doorway LOD cases.

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

CODEMAP.md

@@ -894,6 +894,21 @@ edits keep the full mesh path. The BuildHost commandlet adds height-anchor agree
 sign/size, geometry and per-tile-kind pawn-lag checks; see round 6 in
 [`Standalone/ASSEMBLER_M1_REPORT.md`](Standalone/ASSEMBLER_M1_REPORT.md).
 
+M2 round 3 adds `EVoxelForgeCoreMesherRecipe` / `CoreMesherRecipe` in
+[`Source/VoxelForge/Public/VoxelWorld.h`](Source/VoxelForge/Public/VoxelWorld.h), defaulting to
+`MarchingCubesV1`; `VoxelWorld.cpp` maps the opt-in `WorldAssemblerHybridV1` choice to the Core
+`MesherRecipe` and adds that choice to the Core content identity only while selected. Core extracts
+stable type-2 world-plan boxes as sharp features at LOD0; the production mesher routes tagged
+interior cells through `VoxelHybridSharpMesher.h`, while border-touching cells and LOD1+ remain MC.
+The same-LOD border path stays independent and skirted. `VoxelForgeExploreCommandlet.cpp` owns the
+five production-mesher fixtures, border probes and Core actor collision contacts. BuildHost evidence
+and remaining doorway transition failures are recorded in
+[`Standalone/UNREAL_INTEGRATION_REPORT.md`](Standalone/UNREAL_INTEGRATION_REPORT.md) and
+[`Standalone/Research/WorldAssemblerM2/REPORT.md`](Standalone/Research/WorldAssemblerM2/REPORT.md).
+Likely compile touchpoints are `VoxelWorld.h/.cpp`, `VoxelMarchingCubesMesher.h/.cpp`,
+`VoxelHybridSharpMesher.h`, `Standalone/Core/include/VoxelForgeCore/VoxelForgeCore.h`,
+`Standalone/Core/src/VoxelForgeCore.cpp`, and the editor commandlet/build rules.
+
 [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