MSW Request Mocks for the Browser and Tests

Set up Mock Service Worker so tests and local UI can share one set of handlers. Handlers live next to the API shape, not inside components. API Base URL: [URL] Endpoints to mock first: [LIST WITH METHOD AND A SAMPLE JSON] Auth: [COOKIE | BEARER] Error cases we need: [401, 422 WITH FIELD ERRORS, 500] DELIVER 1) The handler file: success, and one forced error via a query param or a named override so a test can opt in. 2) The test server lifecycle: listen before all, reset after each, close after all. A test that awaits the UI, not a fixed sleep. 3) The browser worker for local dev, gated by an env flag, and the warning so we do not ship the worker to production. Say where the worker file is generated and that it is not a secret. 4) A contract comment: the sample JSON should match the type we already have. If it drifts, which test fails. 5) What not to mock: the module under test. Do not mock fetch globally in a way that hides a request we forgot.