feat(core): ore vein records and a materialAt query, off by default (L50); research R18, R19

Versioned capsule vein records (stable ID, resource ID, endpoints, radius, seeded irregularity) resolved
into the snapshot only when requested, placed beside the route and away from passages, landings and
landmarks (forced-passage control rejected). The bound field table gains materialAt (host + two resource
IDs + Q16 weights) behind a per-tile BVH; mesh export v2 carries per-vertex materials; a measurement-only
yield computes removed resource volume (0 on already-air space). With veins on, every density, mesh,
payload and topology hash is unchanged; demo off: owner hashes identical to L47. fast/medium/full PASS.
Research R18 (cavern-graph planner) and R19 (why FloatingIslands costs ~10x SurfaceWorld).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016dhxM43dnWvUu2B5Ph1iG1

Standalone/Source/StreamingWorld.h

@@ -60,6 +60,8 @@ struct FStandaloneCpuTile
     bool bHasPayloadHash=false;
     uint64 TopologyHash=14695981039346656037ull;
     bool bHasTopologyHash=false;
+    uint64 MaterialHash=14695981039346656037ull;
+    bool bHasMaterialHash=false;
     bool bGenerationFailed=false;
     uint64 MeshPayloadAllocatedBytes=0;
     VoxelForgeCore::TileGenerationStats CoreDiagnostics{};
@@ -846,15 +848,18 @@ private:
             Out.MeshPayloadAllocatedBytes=Result->meshPayloadAllocatedBytes;
             Out.DensityHash=Result->densityHash;Out.MeshHash=Result->meshHash;
             Out.PayloadHash=Result->payloadHash;Out.TopologyHash=Result->topologyHash;
+            Out.MaterialHash=Result->materialHash;
             Out.bHasDensityHash=Result->hasDensityHash;Out.bHasMeshHash=Result->hasMeshHash;
             Out.bHasPayloadHash=Result->hasPayloadHash;Out.bHasTopologyHash=Result->hasTopologyHash;
+            Out.bHasMaterialHash=Result->hasMaterialHash;
             Out.Vertices.reserve(Result->vertices.size());
             for(const auto& Vertex:Result->vertices)
                 Out.Vertices.push_back({
                     {static_cast<float>(Vertex.position.x*0.01),static_cast<float>(Vertex.position.y*0.01),
                      static_cast<float>(Vertex.position.z*0.01)},
                     {static_cast<float>(Vertex.normal.x),static_cast<float>(Vertex.normal.y),
-                     static_cast<float>(Vertex.normal.z)}});
+                     static_cast<float>(Vertex.normal.z)},
+                    Vertex.hostMaterialId,Vertex.resourceMaterialIds,Vertex.resourceWeightsQ16});
             Out.Indices=std::move(Result->indices);
             Out.TriangleSkirtFaceMasks=std::move(Result->skirtFaceMasks);
             if(bProfile)