TypeScript and formatting

Application code, unit tests, and Playwright scenarios use TypeScript 6.0.3 with strict checks. Shared types in src/lib/types.ts describe messages, commerce selections, orders, provider events, and archived threads. Incoming JSON remains runtime-validated. npm run typecheck checks the application and tests; npm run format formats code, and npm run format:check verifies formatting. npm run check runs formatting, lint, types, unit tests, and the production build.