Handle game process exit gracefully

- Added proc_get_status() check in readProcessOutput() to detect when
  the game process has exited
- When process exits, read any remaining output and send to client
- Send system message to notify client that game process has ended
- Close client connection cleanly when process exits
- Prevents server from trying to read/write to dead process pipes
- Prevents "broken pipe" errors and connection hangs

🤖 Generated with Claude Code

Co-Authored-By: Claude <noreply@anthropic.com>

src/Core/GameProcessServer.php

@@ -181,11 +181,56 @@ class GameProcessServer implements MessageComponentInterface
      */
     private function readProcessOutput(ConnectionInterface $conn): void
     {
-        $process = $this->processes[$conn->resourceId] ?? null;
+        $connId = $conn->resourceId;
+        $process = $this->processes[$connId] ?? null;
         if (!$process) {
             return;
         }
 
+        // 检查进程是否还在运行
+        $processStatus = proc_get_status($process['process']);
+        if ($processStatus && !$processStatus['running']) {
+            // 进程已经退出，读取最后的输出并关闭连接
+            echo "[进程] 进程 {$connId} 已退出，状态码: " . $processStatus['exitcode'] . "\n";
+
+            // 尝试读取任何剩余的输出
+            $finalOutput = '';
+            $bufferSize = 8192;
+
+            while (true) {
+                $chunk = @fread($process['stdout'], $bufferSize);
+                if ($chunk === '' || $chunk === false) {
+                    break;
+                }
+                $finalOutput .= $chunk;
+            }
+
+            while (true) {
+                $chunk = @fread($process['stderr'], $bufferSize);
+                if ($chunk === '' || $chunk === false) {
+                    break;
+                }
+                $finalOutput .= $chunk;
+            }
+
+            if ($finalOutput) {
+                $this->sendMessage($conn, [
+                    'type' => 'output',
+                    'text' => $finalOutput
+                ]);
+            }
+
+            // 发送进程退出消息
+            $this->sendMessage($conn, [
+                'type' => 'system',
+                'message' => '游戏进程已退出'
+            ]);
+
+            // 关闭连接
+            $conn->close();
+            return;
+        }
+
         $output = '';
 
         // 在非阻塞模式下，使用fread读取可用数据