Reverts supabase/supabase#46848
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
## Release Notes
**Refactor**
* Standardized 404 error handling across documentation pages to use
Next.js built-in features instead of custom utilities
* Enhanced consistency for missing documentation entries, guides, and
references when users navigate to unavailable pages
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
## I have read the
[CONTRIBUTING.md](https://github.com/supabase/supabase/blob/master/CONTRIBUTING.md)
file.
YES
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **Bug Fixes**
* 404 handling now returns path-aware not-found pages for missing docs
and guides, improving accurate user-facing 404 responses.
* Improved file-missing errors for guides so missing content cases
surface clearer diagnostic info.
* **Chores**
* Enhanced 404 telemetry so missing-path information is recorded for
better monitoring and quicker troubleshooting.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
* fix: remove hidden guide pages from render
Guide pages hidden from nav are still rendered. This change removes them
from both build-time and on-demand rendering.
* fix: build llms script
The build llms script does not run in an environment where React is
available, so it must import from 'common/enabled-features', not from
'common', to avoid errors.
* fix: don't render hidden reference pages
Similar to guides, but for client SDK references. If a page is hidden
from the navigation (its feature flag is toggled off), don't render it
at all. This includes (a) at build time, (b) at request time, and (c) at
crawler request time.
* fix: types
* refactor: reading markdown docs files
Refactor how Markdown docs files are read:
- Reuses the same logic across search index generation & page generation
- Improves the indexed content for search:
- Stops removing MDX components, which often contain useful
information like Admonitions
- Denormalizes Partials and CodeSamples for more complete content
This is a prerequisite step for implementing the "Copy docs as Markdown"
functionality.
Only touches regular guides for now, not federated ones.
* fix: tailwind build error (#37728)
We changed to default to ESM imports a while ago, which means local
builds are now breaking because the Tailwind uses a require. Changed to
CJS for Tailwind config file. (I have no idea how this has been working
on Vercel all this time.)
* style: prettier
