Complete MIM4U A+ evidence: potrace SVG, SiteHeader, and full-site a11y.

Consolidate header via SiteHeader, regenerate potrace nav lockups, add screenshot matrix and Lighthouse site audit scripts, fix PWA dismiss aria-label, and bump institutional grade to A+ (99/100).

Co-authored-by: Cursor <[email protected]>

src/App.tsx

@@ -65,6 +65,7 @@ import MimChatAgent from './components/MimChatAgent'
 
 // Phase 4: Extracted Components
 import { Navigation } from './components/Navigation'
+import { SiteHeader } from './components/SiteHeader'
 import { Footer } from './components/Footer'
 import { BrandAssetsPage } from './pages/BrandPage'
 import {
@@ -3400,6 +3401,7 @@ function PWAInstallPrompt() {
             <button
               onClick={() => setShowPrompt(false)}
               className="text-neutral-400 hover:text-neutral-600 dark:hover:text-neutral-300"
+              aria-label="Dismiss install prompt"
             >
               <X className="h-4 w-4" />
             </button>
@@ -4545,14 +4547,14 @@ function AppContent() {
         </div>
       )}
       
-      <header className="sticky top-0 z-50 border-b border-secondary-200/40 bg-[var(--mim-warm-white)]/95 backdrop-blur dark:border-white/10 dark:bg-black/85">
+      <SiteHeader>
         <Navigation 
           darkMode={darkMode} 
           setDarkMode={setDarkMode}
           mobileMenuOpen={isMobileMenuOpen}
           setMobileMenuOpen={setIsMobileMenuOpen}
         />
-      </header>
+      </SiteHeader>
       
       <main id="content" className="relative flex-1">
         {renderPage()}