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/next.config.mjs

@@ -7,7 +7,7 @@ const nextConfig = {
   basePath: process.env.NEXT_PUBLIC_BASE_PATH || '',
   images: { unoptimized: true },
   pageExtensions: ['js', 'jsx', 'md', 'mdx', 'ts', 'tsx'],
-  transpilePackages: ['@newspaperui/components', '@newspaperui/theme', '@newspaperui/utils'],
+  transpilePackages: ['newspaperui-components', 'newspaperui-theme', 'newspaperui-utils'],
 };
 
 const withMDX = createMDX({