GTA1: GUI Test-time Scaling Agent - Yang, Yan; Li, Dongxu; Dai, Yutong; Yang, Yuhao; Luo, Ziyang; Zhao, Zirui; Hu, Zhiyuan; Huang, Junzhe; Saha, Amrita; Chen, Zeyuan; Xu, Ran; Pan, Liyuan; et al. (International Conference on Learning Representations, 2026)