cmd_chat/__init__.py eagerly imported run_server (sanic/pydantic) and Client,
so any `cmd_chat.*` import — including `python -m cmd_chat.operator` — pulled
the server stack at package init. On a phone/Termux operator that installs only
the operator deps (and where srp may be unbuildable), this failed before the
client's pure-SRP fallback could help.
Make both imports lazy inside main()'s serve/connect branches. The operator
path now imports cleanly with srp/sanic/pydantic all absent (client falls back
to _srp_pure). Add a subprocess regression test to keep it that way.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>