Parses a directory of Health Connect record-type CSVs (one file per type) into
tidy per-modality series. Recognises HeartRate, Steps, OxygenSaturation,
RespiratoryRate and SleepSession (its stages) by filename; the time and
value columns are found by name heuristics, so the common exporter layouts
work without configuration.
Value
A health_connect object: a list with any of heart_rate, steps,
spo2, respiratory_rate (time, value), and sleep (stage intervals
start, end, stage), plus path/tz. spo2 feeds
PhysioWearable::spo2Metrics(), sleep feeds
PhysioWearable::summarizeSleepStages().