Summary

• Adds a ?q= search field to /friends/followers/, /friends/following/, and /friends/mutual/ with the same UI pattern.
• Followers (and Mutual, which reuses the followers template): searches display name, handle/URL, and summary.
• Following: searches display name, user_login, user_url, and description.
• Search runs in-memory after the category filter so the top-of-page totals stay accurate; pagination and filter/sort selections are preserved when searching. Block-theme renderer in includes/class-blocks.php mirrors the same behavior.

Test plan

• /friends/followers/?q=alice narrows the list to matching followers and shows a match count.
• /friends/following/?q=alice narrows subscriptions to matching people/feeds.
• /friends/mutual/?q=alice narrows mutuals (uses followers template with filter=following).
• Filter and sort selections stay active when typing into the search field and submitting.
• The "Clear" link returns to the current filter/sort without the search term.
• Pagination links for searched results include the q parameter.
• composer check-cs passes.

Test in WordPress Playground