feat: front-door menu, Tester/Full modes, How to Play, menu music + ritual

tune: ending gate 70/claimed-2, redemption needs tone>=20 (verified)

feat: retune ending pacing (bad msg 6, good msg 12, neutral msg 12)

feat: screamer flicker + gothic Fear & Hunger framing

fix: child visible early, stains render in real app, flash survives reduced-motion

feat: visibility pass verified by headless screenshots