bun 预设: `event.node.req` 是一个不可读的 unenv 模拟对象 - 原始体代理 (`fetch(url, { body: event.node.req })`) 会抛出 `Readable.asyncIterator 尚未实现!`, 手动流包装读取了一个空体

Inline below rather than a StackBlitz/CodeSandbox link: the starters run Node WebContainers and cannot execute the Bun runtime this bug requires. It is three tiny files with no external services, and it has already been reproduced independently by a Bun maintainer from this exact snippet (Bun 1.4.3, Linux x64 — link in Additional context).