Add return type hint to doRun method

This change adds an integer return type hint to the doRun method in the Application class. This ensures the declaration is compatible with the symfony console input interface.

src/Console/Application.php

@@ -77,7 +77,7 @@ protected function getDefaultInputDefinition(): Console\Input\InputDefinition
         return $inputDefinition;
     }
 
-    public function doRun(Console\Input\InputInterface $input, Console\Output\OutputInterface $output)
+    public function doRun(Console\Input\InputInterface $input, Console\Output\OutputInterface $output): int
     {
         $this->input = $input;