- Added `refsite` attribute to actuators with `site` transmission.
- Such actuators now have a well defined length and can be used for e.g., Cartesian end-effector control.
- Added example models and documentation describing the new feature.
PiperOrigin-RevId: 471561218
Change-Id: I538f09af9600d5c53992c4a9fed325648aab4fa3