wip(assembler): round L11 -- fix 24 m+ crossing crash; near ring ready 2x sooner at spawn

Crash: crossing tiles were coalesced into one huge rectangle, and BuildSpatialBins tried to
resize to ~4.3e17 bytes (std::bad_alloc; the L7 32 m failure had the same cause). Analytic
regions now skip unread dense bins and compile in world-aligned 128-voxel pages, published
together; out-of-range keys error before allocation. 24 m, 32 m and 1 km crossings pass
(1 km: 72 pages, peak RSS 700 MiB).
Spawn: World::isTileShapeFree proves LOD0 SurfaceWorld tiles that never read the cave shape;
those start before shape compile, and all others wait. Reviewer W12 no-hash: near ring 0.337 ->
0.159 s, whole view +2.1%. All SurfaceWorld/FloatingIslands hashes unchanged (W1/W8/W12, both
compilers, forced-overlap run). Unreal VoxelWorld.cpp adapter changed but NOT built here.

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

Standalone/Source/StreamingWorld.h

@@ -60,6 +60,7 @@ struct FStandaloneCpuTile
     bool bHasPayloadHash=false;
     uint64 TopologyHash=14695981039346656037ull;
     bool bHasTopologyHash=false;
+    bool bGenerationFailed=false;
     uint64 MeshPayloadAllocatedBytes=0;
     VoxelForgeCore::TileGenerationStats CoreDiagnostics{};
     std::array<uint64,VoxelDensityProfile::BucketCount> ProfileCycles{};
@@ -834,6 +835,7 @@ private:
             if(!Result)
             {
                 std::fprintf(stderr,"[VoxelForgeCore] tile generation failed: %s\n",Error.c_str());
+                Out.bGenerationFailed=true;
                 Out.WorkerSeconds=std::chrono::duration<double>(FClock::now()-StartTime).count();
                 Out.CompletedAt=FClock::now();return Out;
             }