feat: responsive system, engineering infra, new components, performance

- Section: responsive prop with media query injection
- visual-weights: fontSize clamp() for responsive sizing
- variables.css: add border-radius/shadow/transition/z-index tokens
- ESLint flat config + Prettier + Changeset init
- New components: Footer, NewsSidebar, BreakingNewsBanner
- Image/Figure: loading=lazy, aspectRatio, sizes props

packages/docs/app/examples/blackletter-frontpage/page.tsx

@@ -4,7 +4,7 @@ import {
   Layout, Section, Article, Masthead,
   Headline, Subhead, Kicker, BodyText, Byline, Dateline,
   Figure, PullQuote,
-} from '@newspaperui/components';
+} from 'newspaperui-components';
 
 export default function BlackletterFrontPage() {
   return (