Fix: Route model binding when routes are defined in Action routes() method

[faisuc]

Fixes #316

Route model binding wasn't working when you define routes in an Action's routes() method. So if you had:

public static function routes(Router $router): void
{
    $router->get('/users/{user}', static::class);
}

public function handle(User $user)
{
    // $user was just a string "1" instead of the actual User model
}

The $user parameter would come through as a string instead of the resolved model. Kind of annoying since it works fine when you define routes in routes/web.php.