Fix helpdesk ticket schema drift

[panDing19]

Problem

Some helpdesk fixtures use customer-shaped ticket fields such as customer_id and customer_phone, while the list endpoint assumed every ticket has reporter and department. This can make tasks using customer-shaped helpdesk fixtures fail or lose key ticket context.

Affected tasks

• TGUI08_sms_complaint_helpdesk_mattermost

Fix

• Add a ticket summary helper that accepts both reporter/department-shaped and customer-shaped fixtures.
• Preserve customer_id, customer_phone, and category when present.
• Derive department from organization/customer fields when the explicit field is absent.
• Add a schema drift regression test for customer-shaped tickets.

Tests

• PYTHONPATH=. uv run pytest tests/test_service_schema_drift.py::test_helpdesk_ticket_list_accepts_customer_shaped_fixture -q