Handle TurtleBot3 Gazebo perception input

src/perception_pkg/perception_pkg/launch_spec.py

@@ -6,6 +6,10 @@ def build_perception_commands(config):
     level = config.get("level")
     robot = config.get("robot", "")
     sim_mode = str(config.get("sim_mode", False)).lower()
+    # Gazebo's TurtleBot3 model publishes LaserScan directly. Launching the
+    # pointcloud conversion stack here is both redundant and unsupported.
+    if sim_mode == "true" and robot == "turtlebot3":
+        return cmds
     if level and level != "None":
         cmds.append(["ros2", "launch", f"perception{level}_pkg",
                      "perception.launch.py", f"robot:={robot}", f"sim_mode:={sim_mode}"])