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- scripts/buildBacktest.ts: honest walk-forward validation — params fit on pre-2018 internationals, tested out-of-sample on 7,988 matches (2018-2026) predicting each game from prior data only. Proper scoring (Brier/log-loss/RPS/ accuracy) vs uniform / base-rate / Elo-only baselines + a calibration analysis (reliability bins + ECE). Results: 60% accuracy, RPS 0.171 (beats all baselines), ECE 0.01 (excellent calibration). - Methodology page (/methodology): plain-language model walkthrough, the backtest scorecard, a custom-SVG reliability diagram, and honest limits. Transparency is the differentiator — no market odds, no overclaiming. - ReliabilityDiagram component; 'Model' nav entry. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>