Desired behavior

When users close the Gazebo GUI, the server can sometimes continue running in the background. This, combined with the ability to launch multiple Gazebo simulations, leads to confusion when a new gz sim client instance is started. To improve usability, the Gazebo quick start screen should detect existing running servers and present them to the user before launching a new one. Additionally, enhancing the gz sim -g command to accept a world name argument would allow users to target specific running simulations.

Alternatives considered

Implementation suggestion

Additional context

See #2805