Full-spine backtest harness via _price_from_inputs + range-coverage/calibration/per-segment MAPE. code-reviewer APPROVE. Real prod numbers: overall MAPE 18.4%/bias -1.2%; segments эконом +16% / бизнес -23% / элит -38%; range-coverage 56.6%. Read-only; full suite 2488 passed. Refs #1966.