Uno R3 MCP

My thrust stand for testing RC motors and propellers is an Uno R3 with an HX711 and a load cell, and I wanted Claude to be able to run it. So it can find the board, flash the sketch with arduino-cli, start a test, and read the CSV back over USB. There are ten tools in total, and there's a mock mode so the tests still work the same when the hardware isn't plugged in.