Add search controls and fix search pagination

[akirk]

Summary

• Fix search pagination: Added s to get_minimal_query_vars() so the search term is included in the query vars passed to JavaScript — infinite scroll now correctly loads filtered results instead of unfiltered posts.
• Search-specific controls: When a search is active, replace the regular feed chips (post formats, reactions, hidden items) with search-relevant chips: "Clear search", sort order toggle (oldest/newest first), and compact mode.
• Order parameter support: Added ?order=ASC/DESC query parameter handling in friend_posts_query() so sort order actually takes effect.
• Applied changes consistently to both the classic template (main-feed-header.php) and the block renderer (class-blocks.php).

Test plan

• Visit /friends/?s=someterm and verify search results appear with "Clear search" and "Oldest first" chips
• Click "Oldest first" and verify results reorder and the chip toggles to show both "Oldest first" (active) and "Newest first"
• Scroll down to trigger infinite scroll and verify subsequent pages still contain search-filtered results
• Click "Clear search" and verify return to normal feed with regular chips
• Verify the block-based theme shows the same behavior

Changelog

• Automatically create a changelog entry from the details below

Type

• Fixed

Message

Fix search pagination losing search results on infinite scroll and add search controls (clear search, sort order).

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