Conditional Minimax Regret Design Rules

Implements Conditional Minimax Regret design rules for pilot-informed experimental assignment, as proposed in Yamin (2026) . Includes two-arm, unbounded two-arm, multi-arm, stratified, multiple-outcome, proxy-outcome, and pilot-planning tools. Variance bounds include Maurer and Pontil (2009) empirical-Bernstein bounds and exact Bernoulli confidence bounds.