* Revert "Fix deadlinks (#7880)"

Original commit changeset: d52b3ec

Revert this so we can just fix the real deadlinks.

* Update deadlinks script to take into account redirects

Also check if a redirect exists before erroring.

Fixes the actual broken links.

```
$ yarn deadlinks

yarn run v1.22.22
$ node scripts/deadLinkChecker.js
Checking 177 markdown files...
Fetched 552 React error codes
Loaded 49 redirects from vercel.json

✓ All 1554 links are valid!

✨  Done in 0.86s.
```

* Fix deadlinks take 2

Fixes the actual broken links.

```
$ yarn deadlinks

yarn run v1.22.22
$ node scripts/deadLinkChecker.js
Checking 177 markdown files...
Fetched 552 React error codes
Loaded 49 redirects from vercel.json

✓ All 1554 links are valid!

✨  Done in 0.86s.
```

* [compiler] Rewrite React Compiler Docs

We've received [feedback](https://bsky.app/profile/danabra.mov/post/3lr46ciujjs2r) that the compiler docs are difficult to understand and not prominent enough that people don't realize the compiler is a serious project and is near stable.

This PR rewrites the whole compiler doc section, giving it its own category as well as a standalone reference page.

Preview: https://react-dev-git-pr7868-fbopensource.vercel.app/

When the compiler bails out on code, it  leaves it untouched and unoptimized, so it's always safe for the compiler to bailout.

`panicThreshold` in most cases should be kept as `'none'` unless you want to fail the build on these safe bailouts. It's really only useful during dev when you're working on increasing the coverage of the compiler on your codebase.

I think having it shown here is confusing so I'm opting to just remove it for this particular code example.

Previously the intro was pretty barebones. Fleshed it out a bit more to describe why it might be useful to reach for in a large codebase.

* [compiler] Flesh out incremental adoption intro more

Previously the intro was pretty barebones. Fleshed it out a bit more to describe why it might be useful to reach for in a large codebase.

* [compiler] Add note about gating evaluation

Clarify when the gating function is evaluated.

The Edinburgh meetup group no longer exists and I have been unable to find any other Scottish React groups

Co-authored-by: Fre <[email protected]>

* Updates to Activity docs

* wip

* Updates to Activity docs:

- New intro at top of Reference
- Adds "Deferring hydration of low-priority content" section
- Move "Preventing hidden content from having unwanted side effects" section to Troubleshooting
- Removes SSR section from Troubleshooting

* useLayoutEffect + Tidying up

* Use the same color code step for "visible"

* Tidy

* Typo

* Update section on selective hydration

* Update title

* Clean up props

* Tweak wording

* wip

* wip

* wip

* remove temporary scroll restoration while working on docs

* wip

* wip

…nts (#7939)

Co-authored-by: Sebastian "Sebbie" Silbermann <[email protected]>