standalone: VoxelForgeCore library -- the fast generator behind a clean C++20 API, output unchanged

- Standalone/Core: public header VoxelForgeCore.h (no Unreal types), static library target,
  ResolvedWorldSnapshot (from the schema-v1 JSON), World (compile, generateTile, density/sign,
  point/segment solid, classifyBox), host-supplied JobScheduler (the core starts no threads),
  sequenced, idempotent EditTransaction returning affected tiles per LOD.
- The viewer, benchmarks, edits and audits run on Core; StreamingWorld stays host code.
- Same as round 11: 11 hash rows at W1 and W8, routes 5642/5642, look/passage/far audits pass,
  bad-shell control fails, six fixed captures byte-identical; cold W8 1.025 s vs 1.041 s reference.
- SHARED_CPP_LIBRARY_PLAN.md rewritten for a UBT module compiling the same sources via shims.
Open issue before Unreal: Core's implementation still compiles the Compat stand-ins named like
Unreal types (TArray, FVector...); inside a UE binary that is an ODR clash. Must be namespaced.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MmSoF64BbRFmk9C3p1VsBJ

Standalone/Core/src/StandaloneSnapshotAdapter.h

@@ -0,0 +1,12 @@
+#pragma once
+
+#include "OwnerWorldLoader.h"
+#include "VoxelForgeCore/VoxelForgeCore.h"
+
+#include <memory>
+
+namespace VoxelForgeCore
+{
+    // Private standalone adapter: keeps the compatibility holders behind the public value API.
+    ResolvedWorldSnapshot MakeStandaloneSnapshot(std::shared_ptr<FStandaloneOwnerWorld> owner);
+}