fix: kill horizontal overflow on mobile

Add `overflow-x: clip` to main/section/header/footer/nav so decorative
absolutely-positioned glow elements (dcta-glow, brand-card-glow,
cap-tile-glow) can't bubble their bounds up to body.scrollWidth.
Without this, body extended ~168px past viewport at 360px width,
producing right-side empty gap and horizontal scroll on Android Chrome.

Also stack 2-col grids on narrow viewports in ExclusiveAccessSection,
FounderSection, and IndustryUseCases stats row to prevent cramped
or overflowing content under 640px.

Verified via Playwright at 320/360/375/390/411/414/480 — body.scrollWidth
now equals viewport at all widths.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/robotics/FounderSection.tsx

@@ -48,9 +48,9 @@ export function FounderSection() {
         </div>
 
         <div
+          className="fs-pillars"
           style={{
             display: 'grid',
-            gridTemplateColumns: 'repeat(2, 1fr)',
             gap: '1rem',
           }}
         >
@@ -60,6 +60,17 @@ export function FounderSection() {
           <Pillar value="Future" label="Smart, autonomous, intelligent" />
         </div>
       </div>
+
+      <style jsx>{`
+        .fs-pillars {
+          grid-template-columns: minmax(0, 1fr);
+        }
+        @media (min-width: 640px) {
+          .fs-pillars {
+            grid-template-columns: repeat(2, minmax(0, 1fr));
+          }
+        }
+      `}</style>
     </div>
   );
 }