feat(externalselect): add initialOption + option_groups (vercel/chat#410, #397)#84

patrick-chinchill wants to merge 2 commits intomainChinchill-AI/chat-sdk-python:mainfrom

claude/port-external-select-option-groups-J7S7HChinchill-AI/chat-sdk-python:claude/port-external-select-option-groups-J7S7HCopy head branch name to clipboard