typescript-conventions

# TypeScript Conventions - Use React 19 patterns: functional components, hooks, no class components - Extend existing types rather than type casting: `type UserAdmin = User & { isAdmin: true }` instead of `(user as UserAdmin)` - Component files: PascalCase (`UserProfile.tsx`) - Hook files: camelCase prefixed with `use` (`useLocalStorage.ts`) - Test files live alongside source: `Foo.tsx` -> `Foo.test.tsx` - Use Vitest + React Testing Library for tests (not Jest in Vite projects) - Test behavior with `getByRole`/`getByText`, not `getByTestId` - Import order: React, third-party, local modules, types (enforce with ESLint) - Prefer `interface` over `type` for object shapes that may be extended - Use `satisfies` operator for type-safe config objects