LeRobot unifies Feetech and Dynamixel motor buses with rustypot

LeRobot merges the previously separate FeetechMotorsBus and DynamixelMotorsBus (both based on vendor pure-Python SDKs) into one SerialMotorsBus, now backed by rustypot 1.11.0. Each motor's model definition comes from rustypot's servo definitions, including control table, byte order, sign encoding, baud rate, and model number; on connect, the bus opens rustypot.Bus by model. The two old classes remain for one version as deprecated aliases. A new serial-motors install option is added; the old feetech and dynamixel options still work but point to the same bus. For developers using SO100/SO101, Koch, OMX, LeKiwi, HopeJR, and OpenArm Mini, device code must construct SerialMotorsBus and use names like set_operating_mode("position") instead of vendor enum values. Calibration, firmware checks, and torque control are unified by rustypot; servos without homing offset and operating modes, such as SCS0009, will refuse set_operating_mode() and set_half_turn_homings(). Status packet wait time drops from one second to 50 ms, so a missed reply in a 30 Hz control loop costs only one tick. Teams adding new servos should submit a servo definition to rustypot rather than editing LeRobot's tables.py; LeRobot only reads models included in the installed rustypot Python package, so you must wait for a rustypot release or build from source.