perf: cut CI time, fix CSS chain, fix iPad hero layout, fix contrast

CI:
- Replace `npm run build` with `tsc --noEmit` in test-build job
  → eliminates duplicate Next.js build (~5 min saved per push)
  → Docker deploy job already does the full build

PageSpeed:
- Add `cssChunking: 'loose'` to merge CSS into one chunk and break
  the 84dc7384→3aefc04b render-blocking CSS waterfall chain (450ms mobile)
- Remove @shadergradient/react, @react-three/fiber, three from
  package.json — packages were already unused in code, removes any
  residual bundling risk for chunk 7001

Hero:
- Change lg:flex-row → xl:flex-row so iPad (1024px) stays in column
  layout; the 9.5rem heading overflowed into the image at lg causing
  the photo to be clipped by overflow-hidden on the section
- Update image sizes attribute to match new xl breakpoint
- Fix contrast: "GET IN TOUCH" link text-stone-500 → text-stone-700
  (contrast 3.7:1 → 7:1, now WCAG AA compliant)
- Change text-center/justify-center to xl: variants to match layout

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

next.config.ts

@@ -34,10 +34,12 @@ const nextConfig: NextConfig = {
   experimental: {
     // Tree-shake barrel-file packages in both dev and production
     optimizePackageImports: ["lucide-react", "framer-motion", "react-icons", "@tiptap/react"],
+    // Merge all CSS into a single chunk to eliminate the render-blocking CSS chain
+    // (84dc7384.css → 3aefc04b.css sequential dependency reported by PageSpeed).
+    cssChunking: "loose",
     // Note: optimizeCss (critters) is intentionally disabled — it converts the main
     // <link rel="stylesheet"> to a JS-deferred preload, which PageSpeed reads as a
-    // sequential CSS chain and reports 410ms of render-blocking. Without it both CSS
-    // files load as parallel <link> tags discovered from the initial HTML (~150ms total).
+    // sequential CSS chain and reports 410ms of render-blocking.
     ...(process.env.NODE_ENV !== "production" ? { webpackBuildWorker: true } : {}),
   },