GUI-Actor: Coordinate-Free Visual Grounding for GUI Agents - Wu, Qianhui; Cheng, Kanzhi; Yang, Rui; Zhang, Chaoyun; Yang, Jianwei; Jiang, Huiqiang; Mu, Jian; Peng, Baolin; Qiao, Bo; Tan, Reuben; Qin, Si; Liden, Lars; et al. (Advances in Neural Information Processing Systems, 2025)