fix(2meet-data-optimizer): report entity group name collisions instead of silently dropping

- register_group() keeps the first definition but records a field diff (added/removed/changed) when the same entity/group is re-registered differently; identical re-registration stays silent
- Surface collisions via Site Health (wpdo_entity_group_collisions), the admin Doctor tab, and wp wpdo doctor; warning log throttled to once a day
- Verify: EntityRegistryCollisionTest (7); core unit 613 / integration 432, HP 141/49, WC 10/22 OK
- PR: PR-017

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__( '7 項自動健康檢查：', '2meet-data-optimizer' ) . '</p>'
+		return '<p>' . esc_html__( '8 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>'
@@ -193,6 +193,7 @@ class TMDO_Help_Tabs {
 			. '<li><strong>postmeta_explosion</strong> — ' . esc_html__( 'wp_postmeta > 5M 行', '2meet-data-optimizer' ) . '</li>'
 			. '<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>'
 			. '</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>';
 	}