chore(dynamixel): protocol polish (int default, logging, AX note)

Make the PROTOCOL_VERSION default an int, replace the stray print with a
debug log, and document why AX-series is absent from MODEL_OPERATING_MODES.

src/lerobot/motors/dynamixel/dynamixel.py

@@ -47,7 +47,7 @@ if TYPE_CHECKING or _dynamixel_sdk_available:
 else:
     dxl = None
 
-PROTOCOL_VERSION = 2.0
+PROTOCOL_VERSION = 2
 DEFAULT_BAUDRATE = 1_000_000
 DEFAULT_TIMEOUT_MS = 1000
 
@@ -127,7 +127,7 @@ class DynamixelMotorsBus(SerialMotorsBus):
         self._assert_same_protocol()
         self.port_handler = dxl.PortHandler(self.port)
         self.packet_handler = dxl.PacketHandler(protocol_version)
-        print(f"Using protocol version {protocol_version}")
+        logger.debug(f"Using protocol version {protocol_version}")
         self.sync_reader = dxl.GroupSyncRead(self.port_handler, self.packet_handler, 0, 0)
         self.sync_writer = dxl.GroupSyncWrite(self.port_handler, self.packet_handler, 0, 0)
         self._comm_success = dxl.COMM_SUCCESS

src/lerobot/motors/dynamixel/tables.py

@@ -215,6 +215,8 @@ MODEL_NUMBER_TABLE = {
 
 # {model: available_operating_modes}
 # https://emanual.robotis.com/docs/en/dxl/x/{MODEL}/#operating-mode11
+# Note: AX-series (Protocol 1.0) has no Operating_Mode register; joint vs wheel mode is
+# selected via the CW/CCW angle limits, so it is intentionally absent from this table.
 MODEL_OPERATING_MODES = {
     "xl330-m077": [0, 1, 3, 4, 5, 16],
     "xl330-m288": [0, 1, 3, 4, 5, 16],