await返回以后线程的上下文没有恢复

chan.send_noblock之后，await接受到值，但是之后的线程被改变成新的线程

Start by inspecting the chan.send_noblock and await implementations, then reproduce the reported behavior by recording the thread before sending and after await receives a value. Done means identifying why execution resumes on a different thread and confirming that the original thread context is restored without breaking coroutine behavior.

Written by the indexing model from the issue text.