assets.list lists the robot’s meshes and textures. assets.get returns one
asset’s metadata and a short-lived signed link. assets.urdf returns a signed
link to the URDF with mesh references rewritten.
All three need the role’s assets capability and access to the robot.
Use robots.list to find the robot. Call docs.describe for the full input
schema and possible refusals of each asset action. A signed link expires;
read the action result for its lifetime.