Picker now uses allowsEditing:false + quality:1; picked URI routes through
AvatarCropSheet (Pinch+Pan via RNGH+Reanimated, square crop frame with
corner markers). manipulateAsync crop left as TODO — expo-image-manipulator
not yet installed; sheet passes URI through unchanged until then.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>