feat: initial commit — modified sdsandbox scripts for donkeycar RL training
Key changes vs upstream tawnkramer/sdsandbox:
- Car.cs: per-wheel OverlapSphere barrier detection, CCD mode
- TcpCarHandler.cs: regen_road with RoadBuilder+PathManager fallback,
set_ai_text overlay, BrakeOnUpdate support
- PathManager.cs: self-intersection fix with XZ segment retry loop
- RoadBuilder.cs: BoxCollider per segment, showBarrierMeshes flag
- MapOverlay.cs: minimap refresh on road node position change
Unity version: 6000.4.4f1
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
fcdcb14e57