fix: broaden MariaDB sandbox mode detection

MariaDB 10.11+ can output the sandbox header as /*M!999999\- enable the sandbox mode */. By checking for '999999' and 'sandbox mode' separately, we ensure compatibility across different MariaDB versions and escaping styles.

Author: Evgenii-Zinner

src/DB_Command.php

@@ -827,7 +827,7 @@ public function import( $args, $assoc_args ) {
 			$first_line = fgets( $fp );
 			fclose( $fp );
 
-			if ( false !== $first_line && 0 === strpos( $first_line, '/*!999999\- enable the sandbox mode */' ) ) {
+		if ( false !== $first_line && strpos( $first_line, '999999' ) !== false && strpos( $first_line, 'sandbox mode' ) !== false ) {
 				WP_CLI::log( 'MariaDB sandbox mode directive detected. Skipping it by piping the file content.' );
 				$preamble = $this->get_sql_mode_query( $assoc_args ) . "\n";
 				if ( ! Utils\get_flag_value( $assoc_args, 'skip-optimization' ) ) {