D3D12 Core:
- Add ID3D12Fence1 and fence_value to d3d12_command
- Add fence_event for CPU waiting
- Implement wait() in command_frame for frame sync
- Implement flush() to wait all frames complete
- Add fence_value tracking per frame
- Signal fence at end_frame with incremented value
TestRenderer:
- Call graphics::render() in run()
Documentation:
- Add changelog for Fence sync implementation
- Update D3D12 Wiki with Fence sync section
