vandanarora18/edge-avoidance-bot ? reverse-engineered prompt

Build me a ROS 2 Humble simulation of a small autonomous robot that drives around on a table in Gazebo and never falls off the edge.

I want the robot to have a simple differential drive setup, a downward facing LiDAR that can notice when it is getting close to a cliff, and a behavior that automatically backs up and turns away when an edge is detected. Please wire it so the whole thing can be launched from one command, with the robot model, controllers, simulation world, and the edge avoidance logic all working together.

Keep it clean and modular, with separate pieces for the robot description, control setup, launch files, and the Python brain that handles the sensor data and publishes motion commands. If you need to check current ROS 2 or Gazebo details online while setting it up, go ahead and do that.