docs: clarify demo UX and add Phase 5 test report

  - Update demo-splitting-simple.html: clarify that only loading animation
    is simulated, all S5.js functionality is real (no mocks)
  - Add comprehensive MEDIA_PROCESSING_TEST_REPORT.md documenting all
    Phase 5 tests passed successfully

  Phase 5 Media Processing Foundation: Complete

Author: Developer

demos/media/demo-splitting-simple.html

@@ -229,12 +229,13 @@
     <h1>📦 Code-Splitting Demonstration</h1>
 
     <div class="demo-info">
-      <h3>⚠️ Simulated Demo</h3>
+      <h3>💡 Demo Information</h3>
       <p>
-        This is a simulated demonstration of code-splitting capabilities.
+        This demo uses <strong>real S5.js code</strong> with <strong>real MediaProcessor functionality</strong>.
+        All image processing, WASM initialization, and metadata extraction are fully functional.
+        Only the bundle loading animation is simulated for demonstration purposes (the bundles are pre-loaded in this HTML page).
         In a production environment with proper bundler configuration (Webpack, Rollup, Vite),
-        the actual modules would be loaded dynamically. This demo simulates the loading behavior
-        and shows the expected bundle sizes and performance benefits.
+        the code-splitting would happen automatically at build time.
       </p>
     </div>