Fix Codex issues with Opus

I thought I was going mad, but 5.2 codex isn't running well today

I had to switch to opus 4.5,had issues like:

- writing a lot of wrong code to create nextjs sitemaps even after being given the exact docs on how to do it (opus deleted it all and fixed it in one shot)
- changing things not to do with what I asked (like text/content)
- spending 10 minutes trying to figure out how to copy a tailwind 4 typography examplr from another project (opus did it in <1m)