DISTANCE_SENSOR.signal_quality is always 0

DISTANCE_SENSOR.signal_quality is always 0, so consumers don't have any information about confidence, etc.

I see code to calculate 1-100 confidence from the figure-of-merit, perhaps we can interpret this as signal_quality? I haven't logged this data to see if it's a reasonable idea, but I hope to do so soon.

Locate the code that populates DISTANCE_SENSOR.signal_quality and the existing figure-of-merit confidence calculation. Review how that confidence is derived and validate the proposed interpretation with logged sensor data; done means signal_quality conveys useful confidence information instead of remaining 0.

Written by the indexing model from the issue text.