Add CLAUDE.md with Enix engine architecture reference

[Copilot]

Adds CLAUDE.md to serve as a concise technical reference for AI-assisted development on the Enix Vulkan game engine.

Contents

• Build — CMake commands, named debug configs (CLion/MinGW/MSVC), shader compilation via glslc custom target
• Architecture — entry point, subsystem table (Render/, Core/, Asset/, Input/, UI/), two-pass render pipeline (Blinn-Phong + ImGui), double-buffering, UBO layout
• Conventions — _ member prefix, #pragma once, singleton access pattern, non-copyable render objects, RAII cleanup
• Assets — runtime path resolution relative to bin/
• Third-party — glfw, glm, imgui, spdlog, stb_image, tinyobjloader
• Planned features — PBR, skybox, physics, audio, etc.

All facts verified against source (CMakeLists.txt, Renderer.h, VulkanEngine.h).

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