Standardize nullable type hints to 'null|Type' order

Refactors type hints and docblocks across the codebase to consistently use the 'null|Type' order for nullable types, improving code readability and alignment with modern PHP standards. No functional changes are introduced; this is a documentation and type annotation update only.

Author: huangdijia

src/CommandBuilder.php

@@ -23,7 +23,7 @@
 class CommandBuilder
 {
     /**
-     * @param int|string|array<mixed>|mixed|null $args
+     * @param null|int|string|array<mixed>|mixed $args
      */
     public static function build(mixed $args): string
     {

src/CommandInvoker.php

@@ -39,7 +39,7 @@ public function __construct(protected Connection $connection, protected ?StdoutL
     }
 
     /**
-     * @param int|string|array<mixed>|null $command
+     * @param null|int|string|array<mixed> $command
      */
     public function invoke(mixed $command, int $number): array
     {
@@ -84,7 +84,7 @@ public function ping(float $timeout = 1): string|bool
      */
     protected function receive(Connection $connection): void
     {
-        /** @var array|null $buffer */
+        /** @var null|array $buffer */
         $buffer = null;
 
         while (true) {