Simplify coordinate and sensor definitions in README

Remove implementation commentary, historical metadata notes, transform notation, naming-alias prose and update-scope language. Retain the TCP definitions, units and axes, complete hand-joint order, tactile frame and units, and one front-view coordinate illustration.

README.md

@@ -349,8 +349,6 @@ right_hand_q = row["observation.state"][36:58]
 
 The nominal mapping is `q_urdf = q_dataset`. URDF `origin` defines the joint transform at zero angle, and `axis` defines the positive rotation direction. Do not subtract an episode's first frame as a new zero or apply an additional left/right sign flip. No per-device mechanical zero-offset correction is applied by this export.
 
-Two SDK naming aliases are worth distinguishing: `thumb_DIP` corresponds to URDF `thumb_IP`, and `pinky_CMC_FE` corresponds to URDF `pinky_CMC`. The tactile finger name `little` corresponds to URDF `pinky`. A complete index-to-name mapping for both hands is provided in [hand_joint_mapping.json](assets/coordinate_frames/hand_joint_mapping.json).
-
 ### TCP Pose State and Action
 
 `observation.state.tcp_pose` and `action.tcp_pose` are separate 12D float32 vectors. Components `0:6` contain the left-arm TCP pose and `6:12` contain the right-arm TCP pose.
@@ -365,15 +363,13 @@ The robot base uses a right-handed coordinate system: **+X forward, +Y toward th
 
 The local TCP frames are `left_hand_base_link` and `right_hand_base_link`. In the URDF zero / straight-finger configuration, **+Z points from the wrist toward the fingers, +X points toward the palm / grasping side, and +Y points toward the little-finger side for the left hand and toward the thumb side for the right hand**. These local axes move with the hand. The columns of the decoded rotation matrix give the local TCP X, Y and Z directions expressed in `root_link`.
 
-The corresponding homogeneous transform is `T_root_hand_base`, with `p_root = T_root_hand_base @ p_hand_base` for homogeneous column vectors. This TCP frame is distinct from each fingertip's tactile `elastomer` frame. Existing metadata may still contain `rotation_type: null`; this README explicitly documents the observed TCP convention without rewriting the recorded arrays. The frame definition and agreement with nominal URDF FK do not establish independently measured physical positioning accuracy.
-
 #### Coordinate-frame illustrations
 
-The robot is shown in its configured **HOME pose**, rendered in Isaac Sim from the front. Axis colors are **X red, Y green, Z blue**; left and right refer to the robot's sides. The local hand axes move with the hands. This illustration explains coordinate definitions and does not establish physical calibration accuracy.
+Axis colors are **X red, Y green, Z blue**. Left and right refer to the robot's sides.
 
-![North in HOME pose: base, hand TCP and camera coordinate frames](assets/coordinate_frames/home_front.png)
+![Robot base, hand TCP and camera coordinate frames](assets/coordinate_frames/home_front.png)
 
-Camera axes in this illustration follow the **nominal URDF camera-link frames**, not recording-specific calibrated extrinsics. Camera intrinsics, distortion parameters and calibrated camera-to-hand transforms are outside this documentation update.
+Camera axes follow the URDF camera-link definitions.
 
 ### Video Streams
 
@@ -488,7 +484,7 @@ The dataset provides tactile information in structured numeric and image-based f
 
 The 60D numeric vector is ordered as **left hand first, then right hand**, with each hand ordered **thumb, index, middle, ring, little**. Each consecutive six-value block is `[Fx, Fy, Fz, Tx, Ty, Tz]` for one fingertip.
 
-Each fingertip's six-axis force/torque values are expressed in its corresponding **`*_elastomer` local coordinate frame** in the Sharpa Wave URDF. **Force components `Fx`, `Fy`, `Fz` are in newtons (N); torque components `Tx`, `Ty`, `Tz` are in newton-metres (N·m).** The export preserves the SDK F6 values without an additional coordinate rotation or unit scaling. Dataset `little` channels correspond to the URDF `pinky` finger.
+Each fingertip's six-axis force/torque values are expressed in its corresponding **`*_elastomer` local coordinate frame** in the Sharpa Wave URDF. **Force components `Fx`, `Fy`, `Fz` are in newtons (N); torque components `Tx`, `Ty`, `Tz` are in newton-metres (N·m).** Dataset `little` channels correspond to the URDF `pinky` finger.
 
 The `*_elastomer` frame is the tactile frame. The `*_fingertip` frame is a separate frame used for fingertip position / inverse-kinematics annotations, and `*_hand_base_link` is the hand-base TCP frame; these frames are not interchangeable.