feat(validation): Add enhanced error handling and validation system#64

AnkitaParakh wants to merge 4 commits intogoogle-agentic-commerce:maingoogle-agentic-commerce/AP2:mainfrom

AnkitaParakh:protocol/enhance-error-handlingAnkitaParakh/AP2-shopping-concierge:protocol/enhance-error-handlingCopy head branch name to clipboard