Function bayesian_update 

pub fn bayesian_update(current_confidence: f64, corroborate: bool) -> f64

Bayesian update using Beta-Binomial conjugate prior.

Given a current confidence (interpreted as alpha / (alpha + beta) with total pseudocount), updates the posterior by adding one observation.

• corroborate = true: alpha += 1 (evidence supports the relationship)
• corroborate = false: beta += 1 (evidence contradicts the relationship)