fix: Algolia DocSearch results are duplicated and search bar spans full viewport width

[Jen-Uno]

Current behavior

The Algolia DocSearch integration in the docs site has several issues:

1. Duplicate search results: The DocSearch crawler indexes breadcrumb navigation, heading-level anchors, and same-titled pages from different sections, producing duplicate or near-duplicate results.
2. Search bar spans full viewport width: When the search modal opens, the search input bar stretches across the entire screen instead of staying within the modal. This is caused by docfx's default CSS rule header { position: fixed; top: 0; left: 0; } unintentionally applying to DocSearch's <header class="DocSearch-SearchBar"> element.
3. Search not visible in local builds: The custom TOC template (toc.html.tmpl) that renders the DocSearch button is silently ignored by newer docfx versions, which expect toc.html.primary.tmpl.

Expected behavior

• Search results should be unique and deduplicated
• The search bar should stay within the modal bounds (~560px)
• Search should be visible and functional in local doc builds

How to reproduce

1. Visit the docs site and open DocSearch (Cmd+K)
2. Search for "MVUX" or any common term
3. Observe duplicate results and the search input spanning the full viewport width

Workaround

None

Works on

All platforms (browser-based docs site)

Issues found and fixed

1. Breadcrumb duplicates — The crawler indexed <div id="breadcrumb"> content as separate search records with #breadcrumb anchors. Fixed by filtering those in transformItems and adding data-docsearch-exclude to the breadcrumb template.

2. Same-page heading duplicates — DocSearch creates one record per heading level, so a single page could appear multiple times. Fixed with URL-based deduplication that keeps only the first hit per base page URL.

3. Same-titled different pages — Pages like workshop variants shared identical titles, making results look like duplicates. Fixed by detecting same-titled groups and appending a distinguishing URL path segment to the display text (updating both _snippetResult and _highlightResult so DocSearch actually renders it).

4. Navigation noise in index — The crawler was indexing navbar, footer, and sidebar content. Fixed by adding data-docsearch-exclude to those elements via new template overrides (affix.tmpl.partial, footer.tmpl.partial, breadcrumb.tmpl.partial, and _navbar.tmpl.partial).

5. Search bar spanning full viewport width — docfx's default CSS header { position: fixed; top: 0; left: 0; } was applied to DocSearch's <header class="DocSearch-SearchBar">, pulling it out of the 560px modal. Fixed with a CSS override in main.css.

6. Search not visible in local builds — The custom TOC template was named toc.html.tmpl but docfx 2.73+ expects toc.html.primary.tmpl, so the #docsearch container was silently missing. Fixed by renaming the file and pinning the docfx version.