build: VoxelForge compiles in Unreal 5.7 on Linux (L65); Linux-only Unreal trace timing fields

Linux UE builds failed on the Core wrapper module: the Linux-only PerModuleInline.gen.cpp saw Standalone/Compat
shadow headers instead of the engine's, and WITH_EDITOR was redefined under -Werror. Compat headers now forward
to the engine headers with include_next for generated Linux module TUs (canonical Core TUs opt into the Compat
definitions via CoreNamespacePreamble.h); CoreMinimal.h undefines WITH_EDITOR first. VoxelForgeCore.Build.cs
enables that forwarding and AVX2 on Linux only; VoxelForge.Build.cs disables Unity on Linux only. Portability:
std::int64_t consistently in VoxelContentManager.cpp; grouped &&/|| in VoxelRedefinedDensityField.cpp. Linux-only
trace fields split Core generateTile / mesh copy / RMC stream build. Standalone Clang and GCC whole-view hashes
are unchanged vs 3202193. The Unreal spawn trace is blocked by the owner's new assets (SW route sweep fails).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016dhxM43dnWvUu2B5Ph1iG1

Standalone/Core/src/CoreNamespacePreamble.h

@@ -1,5 +1,9 @@
 #pragma once
 
+// Core implementation TUs opt into the standalone Unreal-shaped compatibility headers. UE's
+// Linux-generated module TUs leave this unset so those same header names forward to the engine.
+#define VFCORE_USE_COMPAT 1
+
 // Every standard or platform header used by the copied implementation must be included before
 // its wrapper opens vfcore::detail. This prevents system declarations from being nested in the
 // private namespace when the implementation includes its Unreal-shaped compatibility headers.