feat(post-list): align list schema with Zibll paging contract

Replace the post_list.list admin contract with a dedicated schema module
using Zibll keys (paging_ajax_s, paging_ajax_ias_s, ajax_trigger,
ajax_nomore, list_orderby, post_list_author/time, target_blank). Runtime
derives numbered/load_more/infinite from those keys and applies list
orderby on main queries without legacy dual-write layers.

inc/classes/class-aksrt-settings.php

@@ -470,7 +470,7 @@ class AKSRT_Settings {
      * Only fires when no explicit orderby is set by URL params or other hooks.
      */
     public static function apply_list_orderby($query): void {
-        AKSRT_Settings_Theme_Search::apply_list_orderby($query);
+        AKSRT_Settings_Post_Display::apply_list_orderby($query);
     }
 
     /**