wip(assembler): round L2 -- the cross-platform hash check can fail; FP contraction changes the world

Clang -ffp-contract=on/fast and GCC's default (fast) all change the density hash on the L1 view;
contraction off reproduces L1 (= Windows S13) at W1/W12. Seed sweep: 48 FloatingIslands seeds and
14 effective SurfaceWorld seeds (34 of 48 fell on a seed-independent cube) match across Clang/GCC
and W1/W12. Standalone gains --seed/--recipe/--render-distance-chunks (viewer + headless) and a
Windows replay script. Linux standalone workers get 32 MiB pthread stacks (TLS is 17.3 MiB/thread),
so no external stack limit is needed. No Core or world-output change; MSVC compile unverified.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Standalone/Source/StreamingWorld.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include "WorldMesher.h"
+#include "StandaloneWorkerThread.h"
 #include "VoxelForgeCore/VoxelForgeCore.h"
 
 #include <condition_variable>
@@ -11,10 +12,12 @@
 #include <chrono>
 #include <cmath>
 #include <cstdint>
+#include <cstdio>
 #include <cstring>
 #include <deque>
 #include <functional>
 #include <fstream>
+#include <limits>
 #include <unordered_set>
 #include <utility>
 
@@ -509,7 +512,7 @@ public:
             Queue.clear();PriorityTasks.clear();
         }
         Wake.notify_all();
-        for(std::thread& Worker:Workers)if(Worker.joinable())Worker.join();
+        for(FStandaloneWorkerThread& Worker:Workers)if(Worker.joinable())Worker.join();
         Workers.clear();
         std::lock_guard<std::mutex> Lock(Mutex);
         Ready.clear();Outstanding.clear();Desired.clear();Running.clear();
@@ -797,7 +800,8 @@ private:
         {
             VoxelForgeCore::TileGenerationOptions Options;
             Options.bandMinZVoxel=Job.BandZMin;Options.bandMaxZVoxel=Job.BandZMax;
-            Options.hashDensity=bHashDensity;Options.skipUvAndColors=bSkipUvAndColors;
+            Options.hashDensity=bHashDensity;
+            Options.skipUvAndColors=bSkipUvAndColors;
             Options.skipMaterialGroups=bSkipMaterialGroups;Options.skipUv=bSkipUV;Options.skipColors=bSkipColors;
             Options.captureColumnCoordinates=bCaptureColumnCoordinates;
             Options.lod8HorizonInteriorStepVoxels=Lod8HorizonInteriorStepVoxels;
@@ -977,7 +981,7 @@ private:
     mutable std::mutex Mutex;
     std::condition_variable Wake;
     bool bStop=true;
-    std::vector<std::thread> Workers;
+    std::vector<FStandaloneWorkerThread> Workers;
     std::deque<std::function<void()>> PriorityTasks;
     std::vector<FStandaloneTileJob> Queue;
     std::vector<FStandaloneCpuTile> Ready;