fix(2meet-data-optimizer): refuse aeav_only and cleanup on HivePress / WooCommerce sites

- Add TMDO_Promotion_Guard: HivePress models read every meta key with an
  empty-key get_*_meta() and WooCommerce does the same for products (and
  writes stock/sales with direct SQL), so on those sites native meta must
  stay authoritative. Promotion to aeav_only is refused in
  TMDO_Mode_Manager::set() (covers REST, CLI, phases, auto-promoter) for
  post/user/term/comment with HivePress and post/user with WooCommerce;
  TMDO_Post_Migration::cleanup() and the cleanup phase refuse too.
  Demotion stays open; filter tmdo_promotion_guard_allow overrides.
- Admin notice lists guarded entities already in aeav_only with the
  restore-native command (no forced demotion on read).
- Verify: PromotionGuardTest 8 OK; unit 668 OK, integration 480 OK,
  phpcs (phpcs.xml) 0, stan OK; dev36 live: 4 promotions + post-cleanup
  refused, wpdo_bridge_modes unchanged
- PR: PR-053

includes/engine/class-tmdo-mode-manager.php

@@ -140,6 +140,11 @@ final class TMDO_Mode_Manager {
 			);
 		}
 
+		$guarded = TMDO_Promotion_Guard::check_promotion( $entity_type, $new_mode );
+		if ( $guarded ) {
+			return $guarded;
+		}
+
 		$all                 = self::all();
 		$all[ $entity_type ] = $new_mode;