✨ better robot joint loading

assets/cartpole/robot.yaml

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+# Classic cartpole — robot hardware config.
+
+urdf: cartpole.urdf
+
+actuators:
+  - joint: cart_joint
+    type: motor
+    gear: 10.0
+    ctrl_range: [-1.0, 1.0]
+    damping: 0.05

assets/rotary_cartpole/robot.yaml

@@ -0,0 +1,15 @@
+# Rotary cartpole (Furuta pendulum) — robot hardware config.
+# Lives next to the URDF so all robot-specific settings are in one place.
+
+urdf: rotary_cartpole.urdf
+
+actuators:
+  - joint: motor_joint
+    type: motor            # direct torque control
+    gear: 0.5              # torque multiplier
+    ctrl_range: [-1.0, 1.0]
+    damping: 0.1           # motor friction / back-EMF
+
+joints:
+  pendulum_joint:
+    damping: 0.0001        # bearing friction