What MuJoCo says when it refuses.
MuJoCo reports a fatal error by printing a message and not returning; inside a
NIF that would abort the VM. c_src/mj_call.hpp intercepts it and re-throws it
on the Elixir side, where it arrives as this exception — the message is
MuJoCo's own, with the function that raised it in front of it
(mj_step: qpos is not finite).
A RuntimeError escaping from ExMujoco.Native is the same thing before
ExMujoco has re-raised it; call the typed functions instead.