RTL Upgrade Desk - React tests moved off Enzyme and test-utils for React 18 and 19

Upgrade one React test file for React 18 and React 19. Free in your browser: act moved from react-dom/test-utils to react and Simulate turned into fireEvent with its import, the other test-utils APIs mapped to Testing Library, every Enzyme wrapper call (shallow, mount, find, simulate, prop, state, instance, setState, setProps, update) listed with its React Testing Library counterpart and a suggested query for its selector, tests that assert internals flagged, and StrictMode call counts that halve in React 19 marked to re-measure - plus the call table, the migration order and CSVs. Metered runs write the review (each finding decided, what a scan cannot see, the order) and the whole file rewritten as behaviour tests, which the page re-scans. Built on the SkillSafe skills @github/react18-enzyme-to-rtl and @github/react19-test-patterns, from github/awesome-copilot (MIT).