Causal attribution for shutdowns: synthetic DiD applied to internet censorship

When a shutdown happens, we can now answer "what caused it?" with a defensible counterfactual. /v1/sentinel/attribute builds a synthetic control from weighted stable-democracy donors, measures the post-period gap, runs a permutation p-value, and surfaces nearby political events. Method: Arkhangelsky et al. (arXiv:1812.09970), adapted from Internet Society NetLoss (ACM JCSS 2024).