Reproduces the production failure locally so we can iterate in seconds
instead of waiting on deploy cycles across 3 repos and PyPI.
Existing test_node.py / test_tls.py use the system Erlang which is
OTP 24 on most dev boxes (Ubuntu 22.04 default) — silently masks
flag-negotiation and protocol bugs that only surface against OTP 25+.
Adds four docker-backed tests:
- plain dist + hand-coded receive (works on all OTP versions)
- TLS dist + hand-coded receive (works on all OTP versions)
- TLS dist + Elixir GenServer (FAILS on OTP 25, passes on 26)
The last one is the minimum repro of the portal@unsandbox.com failure
mode. Once a fix lands, that test goes green and we know the
production smoke test will too.
Uses --network host to share the host's epmd (Linux-only). Docker mounts
from $HOME/.erldistpy-test/ because snap-confined docker can't see /tmp.
Tests skip cleanly when docker isn't installed.
