#1407 skipped 89 Next Steps links whose targets exist in both guides/
and reference/. Rewrite them as /guides/<name> or /reference/<name>
from the source section so Mintlify+GitHub Pages trailing-slash
redirects no longer 404.
Also retarget three in-page heading anchors to Mintlify's rendered
slugs (data-&-features, reasoner-forward/backward-chaining,
litellm-100+-providers).
Closes#1566
Co-authored-by: Sameer Kadam <sskadam6305@gmail.com>