Add coverage checks and push to full code coverage
Refactors and hardens test coverage infrastructure, with a focus on device-tagged suites and maintainability.
What changed
- Split large sensor device specs into focused domain files (
air_quality,loudness,soil_moisture,bme280,nu40c16,si1145,sensor_plumbing,sensor_cross_cutting) plus shared helpers. - Split jobservice unit specs by responsibility (manager vs service, linux support wiring vs registry wiring).
- Expanded seam/error-path tests across sensors/jobservice/mqtt/camera/servos.
- Updated CI/Makefile/docs to keep strict coverage workflows clear.