Task: Verify business_centre Qt UI end-to-end post-NATS

business_centre's Qt UI works correctly post-NATS migration across list, detail, history, delete, and eventing.

• List window loads and displays records; detail window edit/save round-trips without error; history window shows change history; delete removes the record and preserves history; a change in one connected session appears in a second session without manual refresh; all regressions found are fixed inline or filed as captures.

Rather than a separate pass, this task's acceptance was exercised as part of manual feature-testing during the regenerate/reconcile task (0FCD3745-61CD-4644-BAE2-CBCD994448FE, PR #1552): list window load, detail add/edit/save round-trip, history window, delete, and cross-session eventing were all driven live against a Barclays-provisioned database with two Qt clients, using the Test Scenario: Verify business_centre doc below (PASSED). The RefdataPlugin relocation itself (menu/toolbar under Reference Data, gone from the Party/Organisation area) was also confirmed working throughout that same session, since the scenario was run from the relocated menu entry the whole time.

Manual QA scenarios (scaffolded via compass add test_scenario, run through the QA Validation Runner panel) that verify this task. Link new ones here as they're created; the scenario doc itself links back via its "Verifies task" field.

Verified as part of manual feature-testing during the regenerate/reconcile task (PR #1552): list load, add/edit/save, history, delete, and cross-session eventing all confirmed working against the relocated RefdataPlugin menu entry, via the Test Scenario: Verify business_centre scenario (PASSED). No regressions found.