Refactor asset pipeline: new registry, loader, and runtime
Major overhaul of asset system:
- Split assets into source, .gmeta (JSON), and cooked .imported binaries
- Replaced Asset base class; added TextureAsset, TextureLoader
- AssetManager now uses job-based, dependency-aware loading
- Unified IAssetHandler API; removed legacy handler interfaces
- Updated D3D12 allocator and graphics code for new resource model
- Improved error handling, memory management, and GPU upload logic
- Updated docs and removed obsolete code/interfaces
Misaki
abd5ad74d5