A/B confidence intervals, merchandising banners, and recommendation analytics

Experiments now compute Wilson score confidence intervals on conversion and click-through metrics, so a variant's lift is reported with a real statistical bound instead of a raw percentage that might be noise. Search rules gained banner injection — trigger a banner by query match or facet filter, with priority ordering when more than one could fire — alongside the existing pins, boosts, exclusions and redirects. Recommendation models now report their own analytics: impressions, clicks, click-through rate, add-to-cart and revenue, broken down per model.