P-GenRM: Personalized Generative Reward Model with Test-time User-based Scaling - Zhang, Pinyi; Lin, Ting-En; Wu, Yuchuan; Chen, Jingyang; Wang, Zongqi; Yang, Hua; Zhao, Bing; Huang, Fei; Li, Yongbin; Zhang, Kai (International Conference on Learning Representations, 2026)