fix(rtabmap_slam): release scan mutex on conversion failure

rtabmap_slam/test/README.md

@@ -0,0 +1,37 @@
+# Scan transform recovery regression
+
+`scan_tf_recovery.py` is a standalone ROS 2 integration reproducer for the
+scan-conversion error paths in `CoreWrapper::commonLaserScanCallback`.
+It is not registered with CTest yet.
+
+Source your ROS installation and the workspace containing the RTAB-Map build
+under test. Use an unused ROS domain and run the two cases sequentially:
+
+```bash
+source /opt/ros/jazzy/setup.bash
+source install/setup.bash
+export ROS_DOMAIN_ID=171
+python3 src/rtabmap_ros/rtabmap_slam/test/scan_tf_recovery.py
+python3 src/rtabmap_ros/rtabmap_slam/test/scan_tf_recovery.py --late-tf
+```
+
+Adjust the script path for your checkout layout. Python dependencies are
+`rclpy`, `ament_index_python`, `geometry_msgs`, `nav_msgs`, `sensor_msgs`,
+`sensor_msgs_py`, `std_msgs`, `tf2_ros` and PyYAML.
+
+The script starts the installed `rtabmap_slam/rtabmap` executable, publishes
+odometry and `odom -> base_link`, and begins publishing PointCloud2 data after
+four seconds. The control provides `base_link -> lidar` immediately; `--late-tf`
+withholds it until eight seconds. No simulator, hardware or recorded data is
+required. Parameters and captured logs are written under `/tmp`.
+
+Both cases require a nonempty occupancy grid within 18 seconds and a clean
+process exit after SIGINT. The late-TF case also requires a scan-conversion error
+in the log, ensuring the failure path was exercised. A JSON summary reports the
+map dimensions, conversion failure and process exit code.
+
+On stock Jazzy 0.23.7, the control passes but the late-TF case produces no map and
+requires forced shutdown. With the two missing unlocks added, both pass. The
+patched late-TF case passed five runs, including two using default FastDDS and
+two using UDP-only transport. This reproducer exercises the 3D scan path; the
+analogous 2D error path is fixed by inspection but is not independently tested.