perf(streaming): outer tile classifier off by default; delete mode 2

Owner-approved, on the A/B measured in 83a0e4d: the classifier plus exact validation cost more
than it saved on the game path. With it off, ready p95 is 182 vs 190-195 ms, generation p95 is
125-127 vs 139-141 ms, and density calls drop 18%.

- GVoxelForgeOuterClassifierMode defaults to 0. Mode 1 stays reachable via
  voxel.OuterClassifierMode=1 as an A/B instrument; the clamp is now 0..1.
- Mode 2 (validation samples reused as the mesher core grid) is deleted: the reuse grid,
  FVoxelMesherCoreDensityGrid, GenerateMesh's ReusableCoreGrid parameter, bValidationCoreReused,
  TotalValidationCoreReuseTiles and its log field. It could not fire: it reused the grid only
  when validation disproved a uniform verdict, which never happened, and Mixed tiles never
  validate. The mode-1 validation loop exits early again on the first disagreeing sample.
- All three GenerateMesh call sites checked; the density-count pointer binds after BandVoxHi.

Verified by Codex, checked by me against the logs:
- build ok; the measured process loaded the staged DLL, SHA-256 1024D8CF..04D
- export OBJ SHA-256 unchanged: b3e5f4c3..9b377
- a run WITHOUT the override prints outer_classifier_mode=0 validation_density_calls=0,
  proving the new default took effect
- 841/841 tiles have identical triangle counts between mode 0 and mode 1. The 394 tiles mode 1
  skipped as uniform produce 0 triangles in mode 0, so the strate band cut (applied by the
  mesher, not by validation) was not hiding geometry.

Docs: ARCHITECTURE 8.10, CODEMAP (GenerateTileResult, ClassifyTile) and fable-idea T1.d record
that streaming no longer classifies by default. WORK-NEXT item 1 records the owner's playtest:
he can no longer fall through the world.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VZS94UH8bSsBeg5sZaxe2Y

Source/VoxelForge/Private/VoxelMarchingCubesMesher.cpp

@@ -38,7 +38,6 @@ namespace
 FVoxelMeshData UVoxelMarchingCubesMesher::GenerateMesh(FIntVector OriginVoxels, int32 Step, int32 InCellsPerAxis,
                                                        TArray<uint8>* OutCaptureGrid,
                                                        int32 BandZMinVox, int32 BandZMaxVox,
-                                                       const FVoxelMesherCoreDensityGrid* ReusableCoreGrid,
                                                        int64* OutDensitySampleCount)
 {
     TRACE_CPUPROFILER_EVENT_SCOPE(VoxelForge_MesherGenerateMesh);
@@ -230,13 +229,6 @@ FVoxelMeshData UVoxelMarchingCubesMesher::GenerateMesh(FIntVector OriginVoxels,
     const int32 CellsPerAxis = FMath::Clamp(InCellsPerAxis, 2, CHUNK_SIZE);  // coarse tiles use fewer
     const int32 GridDim      = CellsPerAxis + 1;
     const int32 MDim         = GridDim + 2;            // +1 marge de chaque côté
-    const bool bUseReusableCoreGrid = !OutCaptureGrid
-        && ReusableCoreGrid
-        && ReusableCoreGrid->OriginVoxels == OriginVoxels
-        && ReusableCoreGrid->Step == Step
-        && ReusableCoreGrid->CellsPerAxis == CellsPerAxis
-        && ReusableCoreGrid->Samples.Num() == GridDim * GridDim * GridDim;
-
     // COUPE DE CONTENU PAR STRATE — restreint le maillage (et l'échantillonnage) aux cellules
     // dont l'intervalle Z chevauche la bande [BandZMinVox, BandZMaxVox] (voxels inclusifs).
     // Les tuiles à capture ne sont jamais bandées (niveau 0 — garde-fou ci-dessous).
@@ -541,7 +533,7 @@ FVoxelMeshData UVoxelMarchingCubesMesher::GenerateMesh(FIntVector OriginVoxels,
     // gradient) sont échantillonnées — le reste du tampon reste non initialisé et non lu.
     VoxelDensityProfile::FScopedTimer MesherDensityGridTimer(
         VoxelDensityProfile::EBucket::MesherDensityGrid);
-    const bool bUseOperatorBlock = !bUseSharedDensityGrid && !bUseReusableCoreGrid
+    const bool bUseOperatorBlock = !bUseSharedDensityGrid
         && GVoxelForgeUseOperatorBlock != 0;
     if (bUseOperatorBlock)
     {
@@ -576,14 +568,6 @@ FVoxelMeshData UVoxelMarchingCubesMesher::GenerateMesh(FIntVector OriginVoxels,
                     DensityGrid[LocalIndex] = ReuseGrid->Samples[
                         (SharedZ * ReuseGrid->Dim + SharedY) * ReuseGrid->Dim + SharedX];
                 }
-                else if (bUseReusableCoreGrid
-                    && gx >= 0 && gx < GridDim
-                    && gy >= 0 && gy < GridDim
-                    && gz >= 0 && gz < GridDim)
-                {
-                    DensityGrid[LocalIndex] = ReusableCoreGrid->Samples[
-                        (gz * GridDim + gy) * GridDim + gx];
-                }
                 else
                 {
                     // World voxel = tile origin + grid offset scaled by the cell size (Step).