docs(ap2): clarify ES512 signature scope#618

ShuoRen-TT wants to merge 2 commits into

Universal-Commerce-Protocol:mainUniversal-Commerce-Protocol/ucp:mainfrom

ShuoRen-TT:agent/clarify-ap2-es512-scopeShuoRen-TT/ucp:agent/clarify-ap2-es512-scopeCopy head branch name to clipboard