# Description

<!--
Thank you for your interest in sending a pull request. Please make sure
to check the contribution guidelines.

Link:
https://isaac-sim.github.io/IsaacLab/main/source/refs/contributing.html
-->

Enhance Pink IK Controller with Null Space Posture Control

This PR improves the Pink IK controller integration for better humanoid
robot control and more natural postures.

**Note**: Original this PR was staged in the internal repo (#547). It
has been moved here due to new Github workflow.


## Key Changes
### New Null Space Posture Task
- Added NullSpacePostureTask to enforce postural constraints on
shoulder/waist joints while prioritizing end-effector tasks
- Maintains natural robot poses during manipulation
### Controller Improvements
- Tuned low level PD controller gains
- Support mixed task types (FrameTask + NullSpacePostureTask)
### Testing & Environment Updates
- Redesigned pink controller test script to use JSON-based
configurations to program test motions.
- Updated all environments (PickPlace, NutPour, ExhaustPipe) with null
space control, damping tasks, and improved tracking
- Added `Isaac-PickPlace-GR1T2-WaistEnabled-Abs-v0` env that is
identical to `Isaac-PickPlace-GR1T2-Abs-v0` but enables the Waist DOFs.
- Added target_eef_link_names mapping for clearer link specification

Fixes # (issue)
These changes help fix the following problems from [VDR
feedback](https://docs.google.com/document/d/1saB1QA5r_WlD1l17q7C04WWNltnBW-K0ydI2UB8jxAs/edit?tab=t.0)
- [Enable Waist DOF](https://nvbugspro.nvidia.com/bug/5235527)
- Discourage elbow flare
- Make controller low-latency and low-jerk. **We improved the unit test
for the pink controller and reduced our position and rotation accuracy
tolerance from 30 mm, 10 degrees to 1 mm, 1 degree.**
- Develop metric for controller performance
- Added a flag to disable failure due to joint limits. Previously, any
commanded pose that ended in joint limit violation would result in no
solution and the controlled robot freezing in place. This change gets
the solver to still provide a solution and instead issue a warning for
joint limit violations.

## Screenshots

These controller changes have been tested through the Mimic pipeline
(teleop_se3_agent.py, record/replay_demos.py). Here are videos showing
teleoperation of all three environments working.

### PickPlace-GR1T2-Abs
![IK Improvements - Pick Place
Wheel](https://github.com/user-attachments/assets/98bd5a70-e5fc-4b5b-954a-848c8dbe85d4)

### NutPour-GR1T2
![IK Improvements -
NutPour](https://github.com/user-attachments/assets/b3603dd4-73cb-4ee7-9963-c68a32dffc60)


### ExhaustPipe-GR1T2
![IK Improvements -
ExhaustPipe](https://github.com/user-attachments/assets/28cd1a4b-29cc-402c-9ec4-7082b2c64d98)


### Successfully Trained Robomimic Model Rollout on PickPlace task
For the two robomimic tasks: `Isaac-PickPlace-GR1T2-Abs-v0` and
`Isaac-NutPour-GR1T2-Pink-IK-Abs-v0`, if we collect a new dataset, we
achieve a success rate of 96 and 92% respectively.
![IK Improvements - GR1T2 Waist Enabled Model Rollout
Trimmed](https://github.com/user-attachments/assets/d270e8a8-ed72-41f3-84ac-bdc2c02d190d)
![IK Improvements - GR1T2 Nut Pour Model Rollout
Trimmed](https://github.com/user-attachments/assets/1434721a-5dce-4b76-845a-6ac1379982f5)


## Checklist

- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./isaaclab.sh --format`
- [x] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] I have updated the changelog and the corresponding version in the
extension's `config/extension.toml` file
- [x] I have added my name to the `CONTRIBUTORS.md` or my name already
exists there

<!--
As you go through the checklist above, you can mark something as done by
putting an x character in it

For example,
- [x] I have done this task
- [ ] I have not done this task
-->

---------
Co-authored-by: Kelly Guo <kellyg@nvidia.com>