wip(assembler): round L13 -- one density field for every route (multiplayer determinism fix)

Region pages fell back to the legacy GetDensityAt evaluator while the base shape used the Core
manifest field, so a tile's density (and sometimes mesh) depended on streaming history. Pages
are now bound to their world's base FStandaloneShapeWorld evaluator before publication; density,
lattice, detail, classification and solid queries all delegate to it. WorldAssemblyEvaluatorVersion
5 -> 6. Route-parity audit: fails on L12 (5/5); after the fix 0 mismatches over 87 tile pairs
(base/page, base/native-only, edited, two histories), 56 exact-query pairs, 2.3M page samples,
4 seeds/recipes. Page-tile proof audit: 1,274 blocks, 0 violations. The spawn and island worlds
are unchanged; crossing output changed as intended. Reviewer interleaved spawn: +1.1% (noise).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CSFYgsdW8ejZSyiMf4qRSX

Standalone/Source/VoxelForge/Private/VoxelMarchingCubesMesher.cpp

@@ -122,7 +122,8 @@ FVoxelMeshData UVoxelMarchingCubesMesher::GenerateMesh(FIntVector OriginVoxels,
                                                        const FVoxelSharedDensityGrid* InSharedDensityGrid,
                                                        std::vector<float>* OutDebugDensitySamples,
                                                        FVoxelMarchingCubesStageTimings* OutStageTimings,
-                                                       FVoxelUniformBlockProofAuditStats* OutBlockProofAudit)
+                                                       FVoxelUniformBlockProofAuditStats* OutBlockProofAudit,
+                                                       bool bForceFullDensityCapture)
 {
     TRACE_CPUPROFILER_EVENT_SCOPE(VoxelForge_MesherGenerateMesh);
     const uint64 StageMesherStartCycles=OutStageTimings?FPlatformTime::Cycles64():0;
@@ -865,7 +866,8 @@ FVoxelMeshData UVoxelMarchingCubesMesher::GenerateMesh(FIntVector OriginVoxels,
         // allocating the density grid; no samples are skipped for a tile that can contain
         // geometry, and the final geometry remains byte-identical because this path emits none.
         if (bHaveUniformBlock && bAllRelevantBlocksSame && bAllRelevantBlocksUniform
-            && !(Step == 2 && OutDebugDensitySamples != nullptr))
+            && !(Step == 2 && OutDebugDensitySamples != nullptr)
+            && !(bForceFullDensityCapture && OutDebugDensitySamples != nullptr))
         {
             return MeshData;
         }