Finish the examples-typing sweep with the last non-docs-visible
scripts: `-> None` on the two `trio/` behavior-demo mains (plus a
`trio.TaskStatus` on `hold_lock_forever`) and nursery/portal typing
on `integration/mpi4py/inherit_parent_main.py`.
Leaves `concurrent_futures_primes` (a verbatim stdlib baseline) and
`integration/open_context_and_sleep` (its tractor nursery is
commented out) as-is, and the paren-group `trio.open_nursery()`
bindings unannotated (no clean spot for a preceding annotation).
Completes the examples-typing bullet in #472.
(this patch was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code
Gud Boi
56fbed0be1