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/Compat/Serialization/JsonSerializer.h

@@ -1 +1,6 @@
-#pragma once
+#pragma once
+
+#if defined(VFCORE_COMPAT_FORWARD_HEADERS) && !defined(VFCORE_USE_COMPAT) \
+	&& (defined(__clang__) || defined(__GNUC__))
+#include_next <Serialization/JsonSerializer.h>
+#endif