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">

admin/class-tmdo-help-tabs.php

@@ -184,7 +184,7 @@ class TMDO_Help_Tabs {
 	 * @return string
 	 */
 	private static function content_doctor(): string {
-		return '<p>' . esc_html__( '8 項自動健康檢查：', '2meet-data-optimizer' ) . '</p>'
+		return '<p>' . esc_html__( '9 項自動健康檢查：', '2meet-data-optimizer' ) . '</p>'
 			. '<ol class="wpdo-list-disc">'
 			. '<li><strong>schema_drift</strong> — ' . esc_html__( '所有 v2 表是否存在', '2meet-data-optimizer' ) . '</li>'
 			. '<li><strong>error_budget</strong> — ' . esc_html__( '7 天內 wp_wpdo_errors 行數', '2meet-data-optimizer' ) . '</li>'
@@ -194,6 +194,7 @@ class TMDO_Help_Tabs {
 			. '<li><strong>orphan_zone_rows</strong> — ' . esc_html__( '已 idle 的 module 但 zone 表還有資料', '2meet-data-optimizer' ) . '</li>'
 			. '<li><strong>missing_snapshot</strong> — ' . esc_html__( '在 cutover/cleanup/complete 但 7 天沒 snapshot', '2meet-data-optimizer' ) . '</li>'
 			. '<li><strong>entity_group_collisions</strong> — ' . esc_html__( '同名實體群組被不同外掛以不同欄位註冊（後者被忽略）', '2meet-data-optimizer' ) . '</li>'
+			. '<li><strong>orphaned_entity_groups</strong> — ' . esc_html__( '扁平表還在但已無外掛註冊的群組（已依保存的定義還原以維持可讀）', '2meet-data-optimizer' ) . '</li>'
 			. '</ol>'
 			. '<p>' . esc_html__( '結果有 5 分鐘 transient cache，剛操作完想立刻看新值請等下個週期。', '2meet-data-optimizer' ) . '</p>';
 	}