make sure pdf viewer builds

docs/.vitepress/config.mts

@@ -62,4 +62,10 @@ export default defineConfig({
       md.use(mdInline);
     },
   },
+  vite: {
+    ssr: {
+      noExternal: [],
+      external: ["pdfjs-dist"], // don't bundle it for SSR — leave it browser-only
+    },
+  },
 });