Add 404 handling

.astro/types.d.ts

@@ -1,2 +1 @@
 /// <reference types="astro/client" />
-/// <reference path="content.d.ts" />

src/pages/404.astro

@@ -3,8 +3,6 @@ import Icon from '../components/AstroIcon.astro';
 import BaseLayout from '../layouts/BaseLayout.astro';
 import { getRoadmapIds } from '../lib/roadmap';
 
-export const prerender = true;
-
 const roadmapIds = await getRoadmapIds();
 const legacyRoadmapUrls = [...roadmapIds.map((id) => `/${id}/`), '/roadmaps/'];
 ---

src/pages/[roadmapId]/[...topicId].astro

@@ -10,7 +10,10 @@ export const prerender = false;
 const { topicId, roadmapId } = Astro.params;
 
 if (!topicId || !roadmapId) {
-  return Astro.redirect('/404');
+  Astro.response.status = 404;
+  Astro.response.statusText = 'Not found';
+
+  return Astro.rewrite('/404');
 }
 
 // Handle nested paths by joining the segments
@@ -48,7 +51,10 @@ if (!fs.existsSync(contentPath)) {
   );
 
   if (!fs.existsSync(indexFilePath)) {
-    return Astro.redirect('/404');
+    Astro.response.status = 404;
+    Astro.response.statusText = 'Not found';
+
+    return Astro.rewrite('/404');
   }
 
   contentPath = indexFilePath;