wip(assembler): round L4 -- lazy per-thread caches: 17.3 MiB -> 43 KiB per thread, view 7% faster

VoxelForgeCoreThreadLocal::FLazy<T> (new public header ThreadLocalStorage.h) makes every large
thread_local cache a pointer that heap-allocates on that thread's first use (still worker-private,
lock-free). Static TLS 17.33 MiB -> 43 KiB (initialised image 5.8 MiB -> 21 KiB); worker start
5.2 -> 0.12 ms; idle worker RSS 17.7 MiB -> 52 KiB. Linux workers back to 8 MiB stacks.
World unchanged (L1 hashes Clang off/GCC default, W1/W12; FloatingIslands seed 0).
Reviewer interleaved W12: 2.256 -> 2.091 s. MSVC/UBT not compiled here.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ED33VnqepD4YY6gDAAA832

Standalone/Core/src/WorldAssemblerInternal.h

@@ -1,5 +1,6 @@
 #pragma once
 
+#include "VoxelForgeCore/ThreadLocalStorage.h"
 #include "Json.h"
 #include "VoxelForgeCore/VoxelForgeCore.h"
 
@@ -1367,9 +1368,10 @@ namespace world_assembly_detail
     // qui partagent les bits faibles du hash.
     constexpr std::size_t HeightfieldColumnCacheWays=4;
     constexpr std::size_t HeightfieldColumnCacheSetCount=65536/HeightfieldColumnCacheWays;
-    inline thread_local std::array<HeightfieldColumnCacheEntry, 65536> HeightfieldColumnCache{};
-    inline thread_local std::array<std::uint8_t, HeightfieldColumnCacheSetCount>
-        HeightfieldColumnCacheNextWay{};
+    inline thread_local VoxelForgeCoreThreadLocal::FLazy<
+        std::array<HeightfieldColumnCacheEntry, 65536>> HeightfieldColumnCache;
+    inline thread_local VoxelForgeCoreThreadLocal::FLazy<
+        std::array<std::uint8_t, HeightfieldColumnCacheSetCount>> HeightfieldColumnCacheNextWay;
     inline thread_local HeightfieldColumnCacheStats HeightfieldColumnStats{};
     inline thread_local bool HeightfieldColumnCacheLegacyDirectMapped=false;
 
@@ -1504,6 +1506,8 @@ namespace world_assembly_detail
     inline HeightfieldPointSample CachedColumn(const WorldAssemblyRecipeV1& recipe,
         const WorldAssemblyStratumPlanV1& plan,std::int64_t x,std::int64_t y)
     {
+        auto& cache=HeightfieldColumnCache.Get();
+        auto& nextWay=HeightfieldColumnCacheNextWay.Get();
         HeightfieldColumnCacheEntry* replacement=nullptr;
         if(HeightfieldColumnCacheLegacyDirectMapped)
         {
@@ -1513,8 +1517,7 @@ namespace world_assembly_detail
                 ^std::rotl(static_cast<std::uint64_t>(y)*0xC2B2AE3D27D4EB4Full,23)
                 ^static_cast<std::uint64_t>(reinterpret_cast<std::uintptr_t>(&recipe))
                 ^std::rotl(static_cast<std::uint64_t>(reinterpret_cast<std::uintptr_t>(&plan)),41);
-            replacement=&HeightfieldColumnCache[static_cast<std::size_t>(mixed)
-                &(HeightfieldColumnCache.size()-1)];
+            replacement=&cache[static_cast<std::size_t>(mixed)&(cache.size()-1)];
             if(replacement->recipe==&recipe&&replacement->plan==&plan
                 &&replacement->recipeHash==recipe.contentHash
                 &&replacement->planHash==plan.contentHash&&replacement->x==x&&replacement->y==y)
@@ -1528,7 +1531,7 @@ namespace world_assembly_detail
             std::size_t replacementWay=HeightfieldColumnCacheWays;
             for(std::size_t way=0;way<HeightfieldColumnCacheWays;++way)
             {
-                auto& candidate=HeightfieldColumnCache[first+way];
+                auto& candidate=cache[first+way];
                 if(candidate.recipe==&recipe&&candidate.plan==&plan
                     &&candidate.recipeHash==recipe.contentHash&&candidate.planHash==plan.contentHash
                     &&candidate.x==x&&candidate.y==y)
@@ -1539,11 +1542,11 @@ namespace world_assembly_detail
             if(replacementWay==HeightfieldColumnCacheWays)
             {
                 ++HeightfieldColumnStats.columnConflictMisses;
-                replacementWay=HeightfieldColumnCacheNextWay[set];
+                replacementWay=nextWay[set];
             }
-            HeightfieldColumnCacheNextWay[set]=static_cast<std::uint8_t>(
+            nextWay[set]=static_cast<std::uint8_t>(
                 (replacementWay+1)%HeightfieldColumnCacheWays);
-            replacement=&HeightfieldColumnCache[first+replacementWay];
+            replacement=&cache[first+replacementWay];
         }
         auto& entry=*replacement;
         const auto start=std::chrono::steady_clock::now();
@@ -2036,9 +2039,9 @@ void Heightfield2D::resetThreadColumnCacheStats(bool captureCoordinates, bool cl
     // Les sondes de mesure peuvent vider les entrees d'une tuile avant de comparer deux grilles.
     if(clearCache)
     {
-        world_assembly_detail::HeightfieldColumnCache.fill(
+        world_assembly_detail::HeightfieldColumnCache.Get().fill(
             world_assembly_detail::HeightfieldColumnCacheEntry{});
-        world_assembly_detail::HeightfieldColumnCacheNextWay.fill(0);
+        world_assembly_detail::HeightfieldColumnCacheNextWay.Get().fill(0);
     }
     auto& Stats=world_assembly_detail::HeightfieldColumnStats;
     world_assembly_detail::HeightfieldColumnOctaveDrop=octaveDrop;