feat(observability): Phase-0 baseline-observability package + real-run validation

[yueqin22]

Summary

Adds a Phase-0 ROS 2 (ament_python) observability package for the OOMWOO MVP baseline, so that reproducible-run metadata and the §5.2 KPIs can be captured and reported without hand-rolled scripts.

• metrics.py — framework-agnostic KPI aggregation (LiDAR rate, TF latency quantiles, odometry drift, cmd_vel staleness, bumper events, map free ratio, recovery latency).
• metrics_collector.py — real rclpy node subscribing to the baseline topic surface (/scan /odom /tf /cmd_vel /map /bumper_* /oomwoo_status); degrades gracefully when ros_gz_interfaces is not installed (bumper KPIs disabled until ros-humble-ros-gz-interfaces is present).
• run_metadata.py — captures ROS_DISTRO/RMW/Git SHA/seed/scenario into run_metadata.json.
• scenario_registry.py + config/scenario_registry.yaml — the §5.1 eight baseline scenarios.
• launch/baseline_record.launch.py, scripts/baseline_report.py (dict + CLI), scripts/system_sampler.py (Linux /proc), scripts/run_experiment.sh, scripts/demo_publisher.py + scripts/demo_run.sh for verification without a Gazebo robot.
• test/test_metrics.py (10 logic) + test/test_node_smoke.py (2 node) = 12 tests.

Verification (WSL + ROS 2 Humble)

• colcon build OK; colcon test 12/12 pass.
• metrics_collector runs as a real node fed by synthetic /scan /odom /tf /cmd_vel /map @5Hz; produces DEMO_BASELINE_REPORT.md (scan 5.00 Hz meets target, odom drift ≈1.0, TF p95 ≈15 ms).
• Three node-only bugs caught by the real run and fixed: wrong QoS constant (qos_profile_sensor_data), record_cmd_vel not counting samples, and ros_gz_interfaces import crash → graceful degradation.

Notes / follow-ups

• bumper KPIs need sudo apt-get install ros-humble-ros-gz-interfaces (auto-enabled once present).
• Full Gazebo robot run (EKF+SLAM, boustrophedon, recovery) is a later phase; this PR delivers the baseline-observability foundation only.

See jihua20260826.md §7/§9 for the plan and execution log.

[makers-pet]

Hi @yueqin22 , thank you for the PR!

Would it be possible for you to self-host it - and change the PR to a link to your repo (and a description)?

FYI, my Claude a few things

• package.xml build-system mismatch (real bug): it declares <build_type>ament_python</build_type> but <buildtool_depend>ament_cmake</buildtool_depend>. An ament_python package shouldn't depend on ament_cmake — that'll confuse the build. (Should be no buildtool_depend, or ament_python.)
• Placeholder maintainer: oomwoo-baseline oomwoo-contrib@example.com — wants the real contributor identity.
• rosbag2 undeclared: the description says it "records baseline topics via rosbag2," but there's no rosbag2 exec_depend. If the launch/scripts use it, add the dep.
• Tested on Humble, declares Jazzy: package.xml says Jazzy (good), but verification was WSL + ROS 2 Humble. Worth a Jazzy build/test, and it assumes a topic surface (/oomwoo/status, /bumper_*) that should be checked against the real robot.