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/app/globals.css

@@ -74,15 +74,17 @@ html,
 body {
   margin: 0;
   padding: 0;
+  width: 100%;
+  max-width: 100%;
   min-height: 100vh;
   background-color: var(--color-bg);
   color: var(--color-text-primary);
   font-family: 'Inter', system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
   overflow-x: hidden;
+  overflow-x: clip;
   -webkit-font-smoothing: antialiased;
   -moz-osx-font-smoothing: grayscale;
   direction: ltr !important;
-  unicode-bidi: isolate;
   text-align: left;
 }
 
@@ -713,7 +715,10 @@ html {
   .light-sweep { animation: none !important; opacity: 0 !important; }
 }
 
-html, body { overflow-x: hidden; max-width: 100vw; }
+html, body { overflow-x: hidden; overflow-x: clip; max-width: 100%; }
+
+/* Catch-all guard against horizontal overflow */
+main, footer, nav, section, header { max-width: 100%; overflow-x: clip; }
 
 /* === GLOBAL RESPONSIVE GUARDS === */