CLONE WITH

git clone --recurse-submodules https://github.com/correlllab/arpa_ws.git

After editing robot description (e.g. arpa_description/urdf/tool_holder.xacro):
Rebuild so the sim and MoveIt use the new URDF:

colcon build --packages-select arpa_description
source install/setup.bash

Then relaunch. If you forget to rebuild, the launch will print a reminder.