docs(so101): correct stale roll description in IK-Abs cfg

Roll is an engage-relative swing-twist about the controller's local Z
axis (matching the wrist retargeter), not an absolute twist about fixed
world Z (a pre-rework description).

Author: jiwenc-nv

source/isaaclab_tasks/isaaclab_tasks/contrib/stack/config/so101/stack_ik_abs_env_cfg.py

@@ -65,8 +65,8 @@ def _build_so101_stack_pipeline():
     the controller orientation and forwarded as a dedicated pitch channel into a 4×4 task-space
     IK (3 position + 1 pitch) over 4 joints (shoulder_pan, shoulder_lift, elbow_flex,
     wrist_flex). The controller's roll is
-    recovered separately as an absolute swing-twist about fixed world Z and forwarded as a
-    dedicated wrist-roll channel. The gripper jaw tracks the trigger proportionally (analog),
+    recovered separately as an engage-relative swing-twist about the controller's local Z axis
+    and forwarded as a dedicated wrist-roll channel. The gripper jaw tracks the trigger proportionally (analog),
     and the EE position is clutch-rebased around a captured origin so engaging teleop does not
     teleport the arm.
 
@@ -133,9 +133,9 @@ def _build_so101_stack_pipeline():
     )
 
     # Wrist Retargeter (right hand). Reads the same transformed controller stream and emits
-    # both pitch (absolute in-plane gripper tilt [rad]) and roll (absolute swing-twist about
-    # fixed world Z [rad]). Pitch drives the 4×4 task-space IK (3 pos + 1 pitch); roll drives
-    # wrist_roll directly.
+    # both pitch (absolute in-plane gripper tilt [rad]) and roll (engage-relative swing-twist
+    # about the controller's local Z axis [rad]). Pitch drives the 4×4 task-space IK
+    # (3 pos + 1 pitch); roll drives wrist_roll directly.
     wrist = SO101WristRetargeter(name="wrist", input_device=ControllersSource.RIGHT)
     connected_wrist = wrist.connect(
         {
@@ -210,7 +210,7 @@ class SO101CubeStackEnvCfg(stack_joint_pos_env_cfg.SO101CubeStackEnvCfg):
     absolute end-effector **position + pitch** via a reduced-task IK over 4 joints
     (``shoulder_pan``, ``shoulder_lift``, ``elbow_flex``, ``wrist_flex``), where pitch is the
     absolute in-plane gripper tilt [rad], and drive ``wrist_roll`` directly from the
-    controller's roll (absolute swing-twist passthrough). The resulting action is
+    controller's roll (engage-relative swing-twist about the controller's local Z axis). The resulting action is
     ``[pos_x, pos_y, pos_z, pitch, roll, gripper]``.
     """