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-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>';
 	}