fix(cdn): return 404 for packages not in R2 bucket

micropip iterates index_urls in order and stops at the first 200.
Returning 200 with empty HTML for unknown packages prevented fallthrough
to PyPI. Return 404 instead so micropip continues to the next index.

Author: reecelikesramen

worker/src/index.js

@@ -16,6 +16,8 @@ export default {
       const pkgName = path.slice('/cdn/simple/'.length).replace(/\/$/, '')
       if (!pkgName) return new Response('Not Found', { status: 404 })
       const listed = await env.CDN_BUCKET.list({ prefix: `${pkgName}/` })
+      if (listed.objects.length === 0)
+        return new Response('Not Found', { status: 404, headers: { 'Access-Control-Allow-Origin': '*' } })
       const links = listed.objects
         .map(obj => {
           const filename = obj.key.split('/').pop()