rlmesh_env_server_wait
timeout is seconds (NULL = no deadline). A stopped server sets out_stopped true even when returning its background serve error, which is returned once. Timeout expiry sets false; misuse and invalid inputs leave it untouched.
RLMeshStatus rlmesh_env_server_wait(
RLMeshEnvServer* env_server,
const double* timeout,
bool* out_stopped
)