- add joint_names and joint start indices to config
- publish joint_states only when names configured
- add joint index parameters and member storage
- pass robot_description to action server launch
- add sensor_msgs dependency
- add ClearArmError service and ArmError topic publisher
- add InverseKinematics service using current joint seed
- implement RealRobotDriver joint error handling and IK wrappers
- wire periodic error publishing and service callbacks