Preserve the existing public wildcard surface while adding the lazy
`to_asyncio` submodule to `__all__` and `dir(tractor)`.
Exercise both APIs in cold interpreters and verify normal package
import still leaves `asyncio` unloaded.
Review: PR #478 (goodboy)
https://github.com/goodboy/tractor/pull/478#pullrequestreview-4922213201
(this patch was generated in some part by `opencode` using
`gpt-5.6-sol` (`openai`))
Gud Boi
66ac7863b5