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/Research/WorldAssemblerM3/Linux4/TlsProbeMain.cpp

@@ -0,0 +1,11 @@
+#include "StandaloneTlsProbe.h"
+
+#include <cstdlib>
+#include <string_view>
+
+int main(int argc,char** argv)
+{
+    const int workers=argc>1?std::atoi(argv[1]):12;
+    const std::string_view touch=argc>2?argv[2]:"none";
+    return StandaloneTlsProbe::Run(workers,touch);
+}