StatsPAI: agent-native causal inference, paper-ready

StatsPAI is one import statspai as sp over 1,500+ registered functions for causal inference and applied econometrics, numerically aligned with Stata / R reference implementations, with self-describing schemas and result objects that export to LaTeX / Word / Excel / BibTeX. This skill drives it through the canonical pipeline of an applied empirical paper, in one of three modes (default applied econ; epidemiology; ML-causal), and leaves paper-ready artifacts on disk at every step.