Add line sensors topics

[hello-ola]

This PR adds a ROS2 line sensor pipeline for Stretch 4. It publishes calibrated/projected PixArt line sensor points and filtered hazard outputs so downstream packages can consume either the raw projected data or cleaner obstacle/drop evidence.

How To Test

Run stretch_body_server with line_sensor_loop enbaled by adding this

server:
   subsystems:
     - line_sensor_loop

under robot key.

Launch the line sensor publisher: ros2 launch stretch_core line_sensor.launch.py

Confirm topics exist:

ros2 topic list | grep line_sensor

Expected topics:

  /line_sensor/points
  /line_sensor/obstacle_points
  /line_sensor/small_drop_points
  /line_sensor/debug/source_counts

With debug enabled:

ros2 launch stretch_core line_sensor.launch.py publish_debug:=true

Expected extra topics:

  /line_sensor/debug/raw_obstacle_points
  /line_sensor/debug/spatial_obstacle_points
  /line_sensor/debug/raw_small_drop_points
  /line_sensor/debug/spatial_small_drop_points
  /line_sensor/debug/spray_points

To Visualize:

rviz2 -d ~/ament_ws/install/stretch_core/share/stretch_core/rviz/line_sensor.rviz
What To Look For

• /line_sensor/points should publish projected calibrated points in base_link.
• On normal flat floor, obstacle_points and small_drop_points should be empty or low.
• Put a small obstacle near a line sensor:
  • raw_obstacle should increase.
  • obstacle_points should appear after temporal confirmation.

[hello-robot-shehab]

Works on 4024!

ros2 topic list | grep line_sensoror

/line_sensor/debug/source_counts
/line_sensor/obstacle_points
/line_sensor/points
/line_sensor/small_drop_points