wip(assembler): round L1 -- Linux baseline on abyss: Linux world identical to Windows

Headless Linux benchmark/hash tool (Clang 19 / GCC 14) sharing the viewer's plan builder and
streaming pipeline (moved verbatim into StreamBenchmarkPipeline.h / WorldAssemblyPrototype.h).
Owner Round17 view: density/mesh/payload/topology hashes equal the Windows S13 reference at
W1/W8/W12 (Clang, 3 runs each) and W8 (GCC), with -ffp-contract=off. No output change.
Baseline (i9-12900H, CPUs 0-11, powersave/balance_performance): whole view W8 3.562 s median,
W12 3.512 s, W1 16.555 s; peak RSS < 605 MiB.
Review: the default-stack crash is 17.3 MiB of static TLS per thread (glibc puts it in the
thread stack; HeightfieldColumnCache 6.8 MB), not recursion -- open, after S14.
MSVC compile of the viewer refactor not verified (no MSVC here).

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

CODEMAP.md

@@ -874,8 +874,14 @@ round-2 matched capture source and results are under
 [`Standalone/Research/WorldAssemblerM3/Round2/`](Standalone/Research/WorldAssemblerM3/Round2/).
 `RefineLod8NativeCap` in [`Standalone/Core/src/VoxelForgeCore.cpp`](Standalone/Core/src/VoxelForgeCore.cpp)
 replaces coarse LOD8 ceiling surfaces with the planned 2D cap field while retaining ceiling skirts.
-The standalone SurfaceWorld plan composer and capture/audit entry point live in
-[`Standalone/Source/StandaloneViewer.cpp`](Standalone/Source/StandaloneViewer.cpp).
+The standalone SurfaceWorld plan composer (`AttachRound1WorldAssemblyPrototype`) lives in
+[`Standalone/Source/WorldAssemblyPrototype.h`](Standalone/Source/WorldAssemblyPrototype.h), and the
+streaming benchmark/hash pipeline (`RunPipelinedStreamingBenchmark`, `HashTileRows`) in
+[`Standalone/Source/StreamBenchmarkPipeline.h`](Standalone/Source/StreamBenchmarkPipeline.h); both are
+shared by the D3D11 viewer ([`StandaloneViewer.cpp`](Standalone/Source/StandaloneViewer.cpp), which
+keeps the capture/audit entry points) and the Linux headless tool
+([`StreamBenchmarkHeadless.cpp`](Standalone/Source/StreamBenchmarkHeadless.cpp), built by
+`Standalone/BuildLinux.sh`; see `Standalone/Research/WorldAssemblerM3/Linux1/REPORT.md`).
 
 `RunStandaloneWorldExport` in `VoxelForgeExploreCommandlet.cpp` serializes owner assets on the game
 thread to schema-v1 JSON. The adapter parses it through `ResolvedWorldSnapshot::FromJson` and keeps