v0.5.21

Fixed

• The Replace watch strategy no longer aborts the whole sync when the watch's high-resolution HR cannot be extracted (a 0.5.20 regression, #244). It now keeps the watch activity and merges the sets into it in place, so the workout still syncs and the watch HR is never lost. Only the named-exercise display is dropped when the HR cannot be preserved. HR extraction also tolerates a small clock offset between the Hevy workout window and the watch recording.