fix search index fetch path and add blog.python.org migration note

The command palette was fetching /search-index.json without the base
path prefix, causing 404 on GitHub Pages. Also added a comment in
astro.config.ts noting the site/base values for blog.python.org.

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

Author: JacobCoffee

astro.config.ts

@@ -24,6 +24,9 @@ if (isDev) {
   integrations.push(keystatic());
 }
 
+// When moving to blog.python.org, change site and remove base:
+//   site: "https://blog.python.org",
+//   base: "/",
 export default defineConfig({
   site: "https://jacobcoffee.github.io",
   base: isDev ? "/" : "/python-insider-blog",

src/components/CommandPalette.tsx

@@ -186,7 +186,7 @@ export default function CommandPalette({ open: controlledOpen, onOpenChange }: P
     fetchedRef.current = true;
     setLoading(true);
 
-    fetch("/search-index.json")
+    fetch(withBase("/search-index.json"))
       .then((res) => res.json())
       .then((data: PostEntry[]) => setPosts(data))
       .catch((err) => console.error("Failed to load search index:", err))