Turn on both compiler checks in the root TypeScript configuration, which
apps/web, apps/api, apps/extension, packages/shared and packages/plugin-api
extend, and in the separate Expo configuration of apps/mobile.
No switch statement falls through today. The 19 members that override a
base class member (React error boundaries, the local database recovery
error and the vendored poster badge) now declare `override`; this only
changes type checking and is erased from the emitted JavaScript.