fix: ignore 404s for image files during SSR prerendering

Lesson HTML embeds <img src="waves.png"> relative URLs. Vite rewrites
these client-side but not during SSR prerendering, so the crawler
reports a 404. Add handleHttpError to suppress errors for image assets.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: thomasahle

svelte.config.js

@@ -6,6 +6,15 @@ const base = rawBase.endsWith('/') ? rawBase.slice(0, -1) : rawBase;
 export default {
   kit: {
     adapter: adapter({ fallback: '404.html' }),
-    paths: { base }
+    paths: { base },
+    prerender: {
+      // Lesson HTML embeds <img src="waves.png"> which Vite rewrites client-side
+      // but not during SSR prerendering — the crawler sees the original relative
+      // URL and gets a 404.  Ignore those so the build doesn't fail.
+      handleHttpError: ({ path, referrer, message }) => {
+        if (/\.(png|jpg|jpeg|gif|svg|webp)$/.test(path)) return;
+        throw new Error(message);
+      }
+    }
   }
 };