Agent DOM Builder — 流式界面构建器

Build reliable Agent SSE frontends: streaming Markdown, KaTeX math, safe DOM components, cursor-based reconnect/replay, three-state lifecycle, idempotent cancellation, controlled form/button/card/table components, fault-injection demo server, 62 automated tests. 支持断线续传、停止生成、流式公式与表单组件。