feat: flexiv rizon 4s integration

README.md

@@ -14,7 +14,7 @@
 
 **Robot Control Stack (RCS)** is a flexible, native [Gymnasium](https://gymnasium.farama.org/) wrapper-based robot control interface designed specifically for modern robot learning and Vision-Language-Action (VLA) models. 
 
-It completely unifies **MuJoCo simulation** and real-world physical robot control into a single, seamless API. Currently, RCS natively supports five robots out-of-the-box: **Franka FR3/Panda, xArm7, UR5e, SO101, and I2RT YAM.**
+It completely unifies **MuJoCo simulation** and real-world physical robot control into a single, seamless API. Currently, RCS natively supports six robots out-of-the-box: **Franka FR3/Panda, xArm7, UR5e, SO101, I2RT YAM, and Flexiv Rizon 4s.**
 
 ![RCS Demo](https://raw.githubusercontent.com/RobotControlStack/robotcontrolstack.github.io/refs/heads/master/static/videos/grid.webp)
 

THIRD_PARTY_ASSET_LICENSES.md

@@ -23,6 +23,16 @@ The following directories contain third-party assets:
 - `assets/grippers/robotiq_2f85/`
   Origin: MuJoCo Menagerie `robotiq_2f85/`
   License: BSD-style license reproduced below
+- `assets/robots/rizon4s/`
+  Origin: MuJoCo Menagerie `flexiv_rizon4s/`
+  License: Apache License 2.0
+- `assets/robots/yam/`
+  Origin: MuJoCo Menagerie `i2rt_yam/`
+  License: MIT license reproduced below
+- `assets/grippers/flexiv_grav/`
+  Origin: meshes from Flexiv Robotics `flexiv_description` (https://github.com/flexivrobotics/flexiv_description),
+  MJCF generated from its URDF by `assets/grippers/flexiv_grav/convert_from_urdf.py`
+  License: Apache License 2.0
 - `assets/cameras/d405/`
   Origin: Intel RealSense D405 camera assets distributed via MuJoCo Menagerie RealSense assets
   License: Apache License 2.0 notice reproduced below for the upstream Intel RealSense asset family