test: cover nebula_velodyne_common calibration

[mojomex]

Summary

• add focused unit tests for nebula_velodyne_common
• cover return-mode parsing, status streaming, sensor configuration streaming, and calibration YAML read-write paths
• fix the package public link interface so nebula_core_common headers propagate correctly

Verification

• source /opt/ros/humble/setup.bash && colcon build --packages-select nebula_velodyne_common --symlink-install --mixin debug compile-commands coverage-gcc
• source /opt/ros/humble/setup.bash && colcon test --packages-select nebula_velodyne_common --event-handlers console_direct+

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 40.33%. Comparing base (28d11ee) to head (359d18a).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #429      +/-   ##
==========================================
+ Coverage   39.72%   40.33%   +0.60%     
==========================================
  Files         128      128              
  Lines       10018    10024       +6     
  Branches     4977     4984       +7     
==========================================
+ Hits         3980     4043      +63     
+ Misses       5443     5391      -52     
+ Partials      595      590       -5     

Flag	Coverage Δ
nebula_velodyne_common	97.61% <ø> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[drwnz]

Thanks, looks great! The only ones that don't get tested here are failures in reading or writing the calibration file (bad file path, no file exists, malformed yaml). I don't know what the current actual behaviour is in this case, but a silent fail here is potentially a bad day for integration teams.