Summary

This PR adds a custom DocFX theme so the generated docs have a branded landing page, header, navigation, and footer instead of the default out-of-the-box shell.

Highlights

DocFX UI

• Add a custom template under templates/modularitykit.
• Override the DocFX master layout, navbar, footer, logo, and head partials.
• Add a custom main.css with project branding and layout styling.

Landing page

• Add Docs/Home.md as the docs entry page.
• Update toc.yml so the site opens on the new landing page.
• Keep the package and guide sections visible up front.

Build and publish

• Keep publishing the rendered site to GitHub Pages.
• Build the release binaries before DocFX runs so the metadata stage reads assemblies instead of trying to recompile projects.
• Update the local build instructions to match the publish flow.

Why

The previous DocFX setup rendered correctly but used the default shell. That made the site look like a generic docs dump rather than a branded project site. The custom template makes the landing page and navigation feel like part of the repository instead of an unstyled export.

Using assembly-based metadata also avoids the project-load path that was causing duplicate attribute failures during DocFX metadata generation.

Checks

• dotnet build ModularityKit.Mutator.slnx -c Release
• docfx docfx.json
• git diff --check

Closes

• Follow-up to [Task]: Add API reference publishing from XML docs #52