checkPianoRecipe stacks each hand low-to-high (nearest strictly above,
repeated pc -> octave up) and fails any hand spanning > 15 semitones
(minor 10th, SCHEMA rule 3); errors name style/prog/play/chord/hand/
span; refactored to a pure exported checker surfacing all errors per
recipe. Smoke +6 checks -> 799. Independent gate PASS (injection
surfaces 10 named errors exit 1; weakened gate caught behaviorally).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
vadimwit
b4e8f12539