NOTE: This task should be taken on when max-width and search have been implemented (T249363) and deployed for at least 2 weeks across test wikis and the A/B test has completed (T265333). Current test end date: Nov 4
As part of the max-width layout work (T246420), a `layout-max-width.less` file was created containing all the styles relevant to the max-width work along with a `VectorLayoutMaxWidth` feature flag to make the deployment less risky. While the feature flag is helpful in the short-term, it has a high carrying cost  and will be difficult to maintain in the long-term. The max-width design should just be part of the modern Vector experience (non-configurable) and the feature flag removed as soon as possible following its deploy.
Similarly as part of T249363 a feature flag was added for the search in the header feature.
=== Developer Notes
Most of these styles should be easy enough to merge into `layout.less` or `Sidebar.less`, but there are several pending questions:
1) Should the Less variables found in `layout-max-width.less` be moved to `layout.less` or to `variables.less`? I think @Volker_E was of the opinion that these should be part of `variables.less`.
2) Should the styles pertaining only to history and special pages be split into their own stylesheet and conditionally loaded or be part of `layout.less` (where they load on every page)?
3) Should the breakpoint media queries be moved to `layout.less` or is there a better place to put these?
== QA steps (time sensitive)
Exploratory testing is suggested here.
Load Vector modern on https://en.wikipedia.beta.wmflabs.org/wiki/Main_Page and compare with en.wikipedia.org looking for any visual inconsistencies.
Particularly check at different resolutions.
(Note that it's expected that the version on the beta cluster renders better on smaller screens)
=== Developer sign off
[x] `VectorLayoutMaxWidth` config flag is removed.
[x] `VectorIsSearchInHeader` config flag is removed.
[x] Simplify layout-max-width.less styles, moving into layout.less where applicable.
[x] Fold layout-search-header.less styles into layout-default, removing and cleaning up styles where possible.
 [[ https://codesearch.wmcloud.org/search/?q=VectorLayoutMaxWidth&i=nope&files=&repos= | wmf-config ]] is revised to remove outdated configurations.
Given the max-width is disabled on certain pages, many of the styles currently found in `layout-max-width.less` and the file itself will need to stay
== QA Results - Beta
| **AC** | **Status** | **Details** |
| ----- | ----- | ----- |
| 1 | ❓| T258116#6622397 |