Simplify top-level navigation

[infotexture]

The DITA-OT documentation currently uses a common structure for the HTML and PDF output.

The top-level items appear as “parts” in the PDF ToC. The same topics form first level of the navigation sidebar in the HTML output in the distribution package, and on the project website.

Proposal

As discussed at DITA-OT Day 2024 and recent contributor calls, we're considering simplifying this structure to reduce the number of parts and simplify the navigation menu. This would work better with the upcoming bookmap improvements for PDF theme files, and lay the foundation for alternative navigation approaches in HTML.

As a first step, we could merge several of these items, perhaps like this:

---
config:
  sankey:
    showValues: false
---

sankey-beta

%% source, target, value
Landing Page,DITA Open Toolkit 4.2,1
Release Notes,DITA Open Toolkit 4.2,1
Authoring formats,DITA Open Toolkit 4.2,3
Output formats,DITA Open Toolkit 4.2,7
Installing DITA-OT,Installing, 4
Building output,Publishing,5
Parameters,Configuring,3
Customizing HTML,Configuring,2
Customizing PDF,Configuring,3
Adding plug-ins,Extending,4
Creating plug-ins,Extending,9
Error messages and troubleshooting,Troubleshooting,8
Reference topics,Reference,6
Resources,Reference,2

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Caveats

• This effort would focus primarily on the top level, rather than a complete refactoring of the site IA, which is beyond the scope of what's possible for the next release with the resources we have now.
• Wherever possible, previously shared paths will be preserved, because we know Cool URIs don't change.
• Where path changes are necessary, redirects will be implemented on the project website to ensure previously shared links keep working.