feat: add Teensy communication node

[ericcai32]

Summary

Add ROS 2 node for communicating with the Teensy through a serial port. Apologies for the large PR. Most changes are boilerplate and tests; the important changes are in teensy_node.py and serial_port.py.

Changes

• The majority of code is migrated from teensy_node.py and teensy.py in the sailbot repo.
• Instead of the sailboat_main ROS 2 package, the sailing package will contain reinforcement_learning and teensy subdirectories.
• Fixed bug with the PHYSICAL.MAX_RUDDER_ANGLE constant being set to -25 instead of -45 causing errors in angle conversion math. For an operational clamp, a separate constant should be used.
• Instead of INFO logs, the sending and receiving packets log DEBUG logs that are hidden by default. Warnings on send and receive errors are also throttled to a rate of WARNING_THROTTLE_SECONDS.

Testing

• Added serial driver tests for packet parsing, command encoding, and connection cleanup.
• Added ROS node tests for command forwarding and telemetry publishing.
• Covered serial failures, missing telemetry, invalid polling settings, and shutdown behavior.

Future Work

• Add functionality for Teensy to pass up VectorNav and anemometer readings to RL algo.
• Add functionality for ROS 2 to pass down a latlong coordinate to Teensy for determinstic algo.

[nicoleluo7]

If the Teensy is unplugged or the port is wrong, Teensy() crashes after ROS is already started. This finally never runs, so ROS is never shut down. (which is fine if the whole process dies, but it breaks if a test or another script catches the error and keeps going)

tldr I think it's safer to set teensy_node = None before the try. In finally, only destroy the node if it was created, and always call rclpy.try_shutdown() after that

[nicoleluo7]

When we send a sail angle, we send it as-is. When we read it back, we flip it (90 - angle) - I don't remember if this is the intended behavior? @nizhnerk

[nizhnerk]

Yeah I remember this popping up in sailbot sometime before comp because of a servo issue but it's not right.

[ericcai32]

Changed to draft pending @nizhnerk's code quality changes.