Implements the fit-parsing-hardening change. The shared converter now:
- splits output into <trkseg>s on timer stop/start events, falling back to
record gaps > 5 min, so downstream moving-time never bridges a pause;
- slices records into per-session windows (multisport → one activity, one
segment per session), single-session behavior unchanged;
- validates records: finite/in-range coordinates required, timestamp
required, non-finite altitude dropped (point kept), prefers
enhanced_altitude;
- returns { gpx, sport }, mapping FIT session sport/sub-sport to a Journal
SportType (first session wins), consumed by the Wahoo importer + webhook
and Garmin importer as a fallback when the provider sends no type.
Tests drive the converter via mocked fit-file-parser output (segmentation,
validation, sport mapping, no-GPS) per the chosen fixtures approach.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>