feat: add variant support for subagents (#7138) [alt of #7140]#7156

CasualDeveloper wants to merge 1 commit intoanomalyco:devanomalyco/opencode:devfrom

CasualDeveloper:feat/7138-agent-default-variantCasualDeveloper/opencode:feat/7138-agent-default-variantCopy head branch name to clipboard