spawn-agent: 로컬 코딩 에이전트를 Vercel AI SDK 모델처럼 다루는 어댑터

spawn-agent solves the fragmentation problem of multiple local coding agents (Claude Code, Copilot, Cursor, Gemini CLI, etc.) by wrapping them under a unified Vercel AI SDK interface via the Agent Client Protocol standard. Rather than building a new framework, it layers production-grade operational policies—permission gates, activity watchdogs, process lifecycle management, and capability negotiation—over established standards and scattered CLI assets. For teams using AI SDK, this enables seamless agent switching and reliable multi-turn conversations with deterministic resource cleanup and comprehensive error categorization.