feat(2meet-data-optimizer): guard orphaned flat-table groups

- On init:1, re-register aeav_only groups whose flat table exists and whose definition is in wpdo_registry_meta but no active plugin registers them, so their data stays readable (routing only, never DDL)
- Keys owned by a live group, or with rows in native meta (newer data written while orphaned), are left alone; the native-meta check is cached for a day
- Surface restored groups via Site Health (wpdo_orphaned_entity_groups), the admin Doctor tab, and wp wpdo doctor
- Verify: EntityRegistryRestoreTest (9), OrphanGroupRestoreTest (7); core unit 622 / integration 439, HP 141/49, WC 10/22 OK; dry-run on dev20–22 restores 16/17/4 groups, keeps hp_taxonomy hp_sort_order/hp_icon on native
- PR: PR-018

admin/class-tmdo-admin.php

@@ -2990,7 +2990,7 @@ wpdo.getListings({ per_page: 3 }).then(r => console.log(r));'
 		?>
 		<h2><?php esc_html_e( '健康檢查（Doctor）', '2meet-data-optimizer' ); ?></h2>
 		<p class="description">
-			<?php esc_html_e( '8 項自我診斷檢查：schema 完整性、錯誤預算、hook 衝突、autoload 大小、postmeta 爆量、orphan zone rows、缺少快照、實體群組名稱衝突。', '2meet-data-optimizer' ); ?>
+			<?php esc_html_e( '9 項自我診斷檢查：schema 完整性、錯誤預算、hook 衝突、autoload 大小、postmeta 爆量、orphan zone rows、缺少快照、實體群組名稱衝突、孤兒實體群組。', '2meet-data-optimizer' ); ?>
 		</p>
 		<p>
 			<a class="button" href="<?php echo esc_url( admin_url( 'site-health.php' ) ); ?>">
@@ -3012,6 +3012,7 @@ wpdo.getListings({ per_page: 3 }).then(r => console.log(r));'
 			'wpdo_orphan_zone_rows'        => array( 'check_orphan_zone_rows', __( 'Orphan zone rows', '2meet-data-optimizer' ) ),
 			'wpdo_missing_snapshot'        => array( 'check_missing_snapshot', __( '缺少最近快照', '2meet-data-optimizer' ) ),
 			'wpdo_entity_group_collisions' => array( 'check_entity_group_collisions', __( '實體群組名稱衝突', '2meet-data-optimizer' ) ),
+			'wpdo_orphaned_entity_groups'  => array( 'check_orphaned_entity_groups', __( '孤兒實體群組', '2meet-data-optimizer' ) ),
 		);
 		?>
 		<table class="widefat striped">