What

This PR updates the parent page search functionality to use relevance-based matching when users search for keywords. When a search term is entered, results are now ordered by relevance (how well they match the search term) rather than by menu order, providing more intuitive and useful search results.

Why

Previously, the search used partial/fuzzy matching, which could return results that didn't match the user's intent.

This was especially obvious for sites with large page counts. See: Automattic/wp-calypso#49684

How

• packages/fields/src/fields/parent/parent-edit.tsx: Added orderby: 'relevance' to the search query when fieldValue is not null
• packages/editor/src/components/page-attributes/parent.js: Added orderby: 'relevance' to the search query when fieldValue is truthy

Both implementations now use relevance-based ordering when a search term is provided, ensuring that the WordPress REST API returns results sorted by how well they match the search query, with the most relevant matches appearing first.

Testing Instructions

Prerequisites

• WordPress installation with wp-env running
• At least one hierarchical post type (e.g., Pages)

Test Steps

1. Create test pages:
   • Create a page titled "Services"
   • Create a page titled "About Services"
   • Create a page titled "Our Services Page"
   • Create a page titled "Contact"

OR create a bunch using wp-cli:

alias wp='npx wp-env run cli wp' 
wp post create --post_type=page --post_title="Services" --post_status=publish
wp post create --post_type=page --post_title="About Services" --post_status=publish
wp post create --post_type=page --post_title="Our Services Page" --post_status=publish
wp post create --post_type=page --post_title="Contact" --post_status=publish
....

2. Test relevance-based ordering in Post Editor:

   • Open the Post Editor
   • Create or edit a page
   • Open the Page Attributes panel
   • Click on the Parent dropdown/combobox
   • Type "Services" in the search field
   • Expected: Pages containing "Services" should appear, ordered by relevance:
     • "Services" should appear first (exact match)
     • "About Services" and "Our Services Page" should appear next (close matches)
     • "Service Information" should appear if it matches (partial match)
   • Clear the search and type "About"
   • Expected: "About Services" should appear first (most relevant match)

3. Test relevance-based ordering in Dataviews/Fields:

   • Navigate to the Pages list view (if using the new fields interface)
   • Edit a page
   • In the Parent field, start typing a page name
   • Expected: Search results should be ordered by relevance, with the most relevant matches appearing first

4. Test ordering behavior:

   • When no search term is entered, verify results are still ordered by menu_order (default behavior)
   • When a search term is entered, verify results switch to relevance ordering
   • Verify that exact matches appear before partial matches
   • Verify that pages starting with the search term appear before pages containing the term elsewhere

5. Verify no regression:

   • Ensure that when no search term is entered, the full list of parent pages is still displayed correctly
   • Verify that the hierarchical tree structure is maintained when not searching
   • Confirm that the current parent page is always included in the options list
   • Verify that the getItemPriority function still works correctly for client-side sorting of results