Adjust `basic_echo_server()` default sequence len to avoid the race
where the 'tell_little_bro()` finished streaming **before** the
echo-server sub is cancelled by its peer subactor (which is the whole
thing we're testing!).
Deats,
- bump `rng_seed` default from 50 -> 100 to ensure peer
cancel req arrives before echo dialog completes on fast hw.
- add `trio.sleep(0.001)` between send/receive in msg loop on the
"client" streamer side to give cancel request transit more time to
arrive.
Also,
- add more native `tractor`-type hints.
- reflow `basic_echo_server()` doc-string for 67 char limit
- add masked `pause()` call with comment about unreachable
code path
- alphabetize imports: mv `current_actor` and `open_nursery`
below typed imports
(this commit msg was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code