fix(docs): fix Google indexing by resolving soft 404s and adding SEO files

The SPA fallback (`not_found_handling = "single-page-application"`) caused
Cloudflare to serve index.html with 200 OK for all non-existent URLs,
including /robots.txt and /sitemap.xml. This created massive soft 404
issues that prevented Google from indexing the site.

- Change not_found_handling to "404-page" so unknown URLs get proper 404s
- Add robots.txt allowing all crawlers and pointing to sitemap
- Add sitemap.xml listing all documentation pages
- Generate 404.html in the build so Cloudflare serves it for missing pages

https://claude.ai/code/session_013CBiA8ohEEwKH5DLwjKqkt

Author: claude

packages/docs/public/robots.txt

@@ -0,0 +1,4 @@
+User-agent: *
+Allow: /
+
+Sitemap: https://static.funstack.work/sitemap.xml

packages/docs/public/sitemap.xml

@@ -0,0 +1,48 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
+  <url>
+    <loc>https://static.funstack.work/</loc>
+  </url>
+  <url>
+    <loc>https://static.funstack.work/getting-started</loc>
+  </url>
+  <url>
+    <loc>https://static.funstack.work/getting-started/migrating-from-vite-spa</loc>
+  </url>
+  <url>
+    <loc>https://static.funstack.work/faq</loc>
+  </url>
+  <url>
+    <loc>https://static.funstack.work/api/funstack-static</loc>
+  </url>
+  <url>
+    <loc>https://static.funstack.work/api/defer</loc>
+  </url>
+  <url>
+    <loc>https://static.funstack.work/api/entry-definition</loc>
+  </url>
+  <url>
+    <loc>https://static.funstack.work/learn/how-it-works</loc>
+  </url>
+  <url>
+    <loc>https://static.funstack.work/learn/rsc</loc>
+  </url>
+  <url>
+    <loc>https://static.funstack.work/learn/optimizing-payloads</loc>
+  </url>
+  <url>
+    <loc>https://static.funstack.work/learn/lazy-server-components</loc>
+  </url>
+  <url>
+    <loc>https://static.funstack.work/learn/defer-and-activity</loc>
+  </url>
+  <url>
+    <loc>https://static.funstack.work/learn/file-system-routing</loc>
+  </url>
+  <url>
+    <loc>https://static.funstack.work/advanced/multiple-entrypoints</loc>
+  </url>
+  <url>
+    <loc>https://static.funstack.work/advanced/ssr</loc>
+  </url>
+</urlset>

packages/docs/src/entries.tsx

@@ -20,9 +20,16 @@ function pathToEntryPath(path: string): string {
 }
 
 export default function getEntries(): EntryDefinition[] {
-  return collectPaths(routes).map((pathname) => ({
+  const entries = collectPaths(routes).map((pathname) => ({
     path: pathToEntryPath(pathname),
     root: () => import("./root"),
     app: <App ssrPath={pathname} />,
   }));
+  // Generate a 404.html so Cloudflare can serve it with a proper 404 status
+  entries.push({
+    path: "404.html",
+    root: () => import("./root"),
+    app: <App ssrPath="/404" />,
+  });
+  return entries;
 }

packages/docs/wrangler.toml

@@ -5,4 +5,4 @@ compatibility_date = "2026-02-18"
 
 [assets]
 directory = "./dist/public"
-not_found_handling = "single-page-application"
+not_found_handling = "404-page"