Fix critical bugs and improve hardware interface robustness

[Copilot]

Several bugs were rendering the Arduino IMU node non-functional and a CAN motor control method would crash at runtime. Additionally, the codebase lacked runtime dependency declarations, had a permanently disabled IMU launch, and had no CI.

Critical Bug Fixes

• arduino_interface.py: finally block inside the read loop closed the serial port after every single line — the node could only ever read one IMU message. Replaced the blocking while loop in __init__ with a create_timer(0.02, ...) callback; cleanup moved to destroy_node()
• can_joint.py: test_movement() referenced bare axisID (NameError at runtime) instead of self.axisID

Arduino Interface Improvements

• Serial port and baud rate are now ROS 2 parameters (serial_port, baud_rate) instead of hardcoded values
• json.JSONDecodeError caught per-frame so bad serial data logs a warning and continues rather than crashing
• Uses non-deprecated get_logger().warning() instead of warn()

Package Metadata

• pilla_hw/package.xml: Added missing exec_depend entries — rclpy, sensor_msgs, trajectory_msgs, std_msgs, std_srvs, diagnostic_msgs, python3-serial
• pilla_teleop/package.xml: Upgraded to package format 3; replaced deprecated run_depend with exec_depend; added missing champ_msgs dependency

Launch Files

• odrive_nodes_launch.py: Replaced 12 copy-pasted Node(...) blocks with a list comprehension
• champ_pilla_launch.py: Uncommented the Arduino IMU launch (had been disabled since initial commit); added use_imu launch arg with IfCondition; use_joy is now a launch arg instead of hardcoded 'true'

Arduino Firmware

• Corrected misleading comment: // 20ms for 50Hz → // 10ms for 100Hz to match interval = 10

CI

• Added .github/workflows/ci.yml with two jobs: flake8 --select=F (undefined names/variables) on Python sources, and a CAN library import validation job

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