Thinking in Structures: Evaluating Spatial Intelligence through Reasoning on Constrained Manifolds. - Chen Yang 040; Guanxin Lin; Youquan He; Peiyao Chen; Guanghe Liu; Yufan Mo; Zhouyuan Xu; Linhao Wang; Guohui Zhang; Zihang Zhang; Shenxiang Zeng; Chen Wang 068; et al. (CoRR, 2026)