std: integrate Io.Threaded with environment variables
* std.option allows overriding the debug Io instance
* if the default is used, start code initializes environ and argv0
also fix some places that needed recancel(), thanks mlugg!
See #30562
3c2f5adf41Andrew Kelley committed on 12/24/2025, 6:15:12 AMparent86e9e32