feat(2meet-data-optimizer): warn when HivePress / WooCommerce run without their AddOn

- TMDO_Compatibility::missing_integration_addons() reports active HivePress / WooCommerce whose AddOn bootstrap class is absent
- Surface it as Site Health test wpdo_missing_integration_addons (also on the admin Doctor tab) and an administrator notice (TMDO_Missing_Addons_Notice)
- Verify: MissingIntegrationAddonsTest (5, class stand-ins in separate processes); core unit 651 / integration 449, HP 148, WC 10 OK; read-only check: dev20/21 HivePress+WooCommerce, dev22 HivePress, others clean
- PR: PR-035

includes/class-tmdo-compatibility.php

@@ -68,6 +68,26 @@ class TMDO_Compatibility {
 		return class_exists( 'WooCommerce' );
 	}
 
+	/**
+	 * Integrations that are active while their AddOn is not.
+	 *
+	 * Core does not know these plugins; their fields are only optimised by the
+	 * matching AddOn. The AddOn is detected by its bootstrap class, which its
+	 * main file declares as soon as the plugin loads.
+	 *
+	 * @return array<string, string> Plugin name → AddOn plugin slug.
+	 */
+	public static function missing_integration_addons(): array {
+		$missing = array();
+		if ( self::is_hivepress_active() && ! class_exists( 'TMDO_HP_Bootstrap' ) ) {
+			$missing['HivePress'] = '2meet-data-optimizer-hivepress-addon';
+		}
+		if ( self::is_woocommerce_active() && ! class_exists( 'TMDO_Woocommerce_Bootstrap' ) ) {
+			$missing['WooCommerce'] = '2meet-data-optimizer-woocommerce-addon';
+		}
+		return $missing;
+	}
+
 	/**
 	 * Is LatePoint plugin active? (v2.5.0 M16 polish — for module detector.)
 	 *