Clarify end_call_reasons placement on create and update assistant
The OpenAPI spec listed end_call_reasons on both the top-level request body (via Agent_model) and the nested agent object. Only agent.end_call_reasons is applied when creating or updating an agent; a top-level end_call_reasons field is ignored and does not return an error.
The duplicate top-level field was removed from the documented create/update request schema (via Agent_model). GET /assistants and GET /assistants/{model_id} responses still document an optional top-level end_call_reasons on each assistant object where the API may return it, with a note that configuration must use agent.end_call_reasons on writes. The end_call_reasons field on the Agent schema states this explicitly. The End-Call Reasons guide was updated with a full request example.
Updated references: