- Add FenceStatus enum for status query
- Add m_sync (GLsync) for OpenGL fence synchronization
- Add Signal(value) overload with fence value
- Add Wait(timeoutNs) with timeout support
- Add GetStatus() for async status check
- Add GetCompletedValue() and GetCurrentValue()
- Implement using glSync for proper GPU synchronization
- Replace glFinish blocking with glClientWaitSync