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/ExclusiveAccessSection.tsx

@@ -93,9 +93,9 @@ export function ExclusiveAccessSection() {
 
         {/* Right premium showroom grid */}
         <div
+          className="exa-tiles"
           style={{
             display: 'grid',
-            gridTemplateColumns: 'repeat(2, minmax(0, 1fr))',
             gap: '0.875rem',
             minWidth: 0,
           }}
@@ -125,6 +125,14 @@ export function ExclusiveAccessSection() {
         .exa-grid {
           grid-template-columns: 1fr;
         }
+        .exa-tiles {
+          grid-template-columns: minmax(0, 1fr);
+        }
+        @media (min-width: 640px) {
+          .exa-tiles {
+            grid-template-columns: repeat(2, minmax(0, 1fr));
+          }
+        }
         @media (min-width: 1024px) {
           .exa-grid {
             grid-template-columns: minmax(0, 0.95fr) minmax(0, 1.05fr);