Fix Linux/clang build and runtime issues

[Pursche]

Compile fixes for clang (MSVC-isms):

• offsetof(Type, Type::member) -> offsetof(Type, member) in CulledRenderer, JoltDebugRenderer, ModelRenderer (standard offsetof takes a member designator; the qualified form is an MSVC extension)
• LightRenderer.h: add missing RenderGraphBuilder forward declaration
• UpdateUnitEntities.cpp: fix tracy include case (tracy/Tracy.hpp); only resolved on case-insensitive filesystems

Runtime fixes:

• Application.cpp: open PACT storage at Data/Pact (was data/pact, which only worked on case-insensitive filesystems; with FallbackToInit the game silently created and read an empty archive on Linux)
• FactionUtil.cpp: Reaction perception override was unreachable without a local player set; return the override before the local-player early-out (matches the override-is-absolute semantics the tests expect)

Shader fixes:

• Model/Terrain Draw.vs.slang: SV_ClipDistance must be float or float[] (slang 2026.13 enforces this); use float[4] with element-wise writes

Build system fixes:

• ProjectUtil.lua: linkgroups + $ORIGIN rpath on Linux, fix executable extension map (no extension on Linux)
• ShaderCookerStandalone.lua: cook shaders as a post-build step on non-Windows; premake's gmake backend generates no build target for Utility projects, so the Shaders project's prebuild never ran
• Shaders.lua: adapt cooker invocation to the extension-map fix
• Submodules/Engine: bump to LinuxBuildFix (Linux/clang build and runtime fixes)