Draft: feat(navigation): Revise navigation page

What does this MR do?

Since overhauling the navigation in 16.0, Pajamas has not been updated to reflect the guidelines, structure, and behavior of the new navigation experience. This merge request updates the documentation for the navigation pattern in GitLab. It introduces a new layout with two main versions of the navigation structure: one for authenticated users and one for visitors. The updated documentation also includes more detailed guidelines and principles for designing the navigation, as well as information on messaging changes to users. Additionally, it provides more specific details on the behavior of the navigation sidebar, pinned items, collections, and breakpoints.

Before	After

Does this MR meet the acceptance criteria?

• The MR title and commit messages meet the Pajamas commit conventions.
• The “What does this MR do?” section in the MR description is filled out, explaining the reasons for and scope of the proposed changes, per “Say why not just what”.
  • For example, if the MR is focused on usage guidelines, addressing accessibility challenges could be added in a separate MR.
• Relevant label(s) are applied to the MR.
• The MR is added to a milestone.
• If creating a new component page from scratch, it follows the page template structure.
• Content follows the Pajamas voice and tone guidelines, falling back on the GitLab Documentation Style Guide when needed.
• Related pages are cross-linked, where helpful. Component pages have related components and patterns defined in their Markdown front matter.
• If embedding a Figma file, it follows the Figma embed guide.
• Review requested from any GitLab designer or directly from a maintainer or trainee maintainer.

Links

Pajamas documentation updates based on navigati... (#1501 - closed)