refactor: no comments left - one-line module docstrings, contracts on public fields only; jobs/job.py; example config and README

src/beaver_gateway/conversations/kinds.py

@@ -1,4 +1,4 @@
-"""Conversation kinds (§3.1) as one closed type for agents, frontends, service."""
+"""Conversation kinds as one closed type for agents, frontends, service."""
 
 from __future__ import annotations