Smoke run 4 crashed with AttributeError: 'SessionForTasksCreateRequest'
object has no attribute 'config' when main-pm called open_session.
The service _build_session_request reads req.config.max_message_count
(model has nested config). The gateway was passing the API schema
SessionForTasksCreateRequest (flat fields, no config attribute at all)
— so `req.config` blew up with AttributeError, not the safer None.
Fix: gateway now constructs SessionForTasksCreate (the model) with the
enum-typed relationship_type, matching what the route at
roboco/api/routes/sessions.py:230 does. Unknown relationship strings
fall back to DISCUSSION.
Two regression tests pin the contract: service receives the model;
invalid relationship_type defaults to DISCUSSION.
Renn F
7430c88f63