feat(cart): Embedded protocol transport binding for cart capability + reauth mechanism in ECP#244

Draft

jingyli wants to merge 3 commits intoUniversal-Commerce-Protocol:mainfrom

jingyli:clean-cart-embedded

Commits on Mar 7, 2026

Add back ECaP proposal based on aligned approach and preserve symmetry with ECP by also introducing ec.auth.
jingyli
committed
Add new proposals around reauth and embedded capabilities negotiation.
jingyli
committed
Merge branch 'Universal-Commerce-Protocol:main' into clean-cart-embedded
jingyli
authored