v0.6.4

Fixed

• Replace now works on watch activities whose FIT file contains a non-UTF-8 byte in a string field (#244). Some devices (a Garmin Fenix 7 Pro was the first confirmed) write a manufacturer or product name with a byte that isn't valid UTF-8, and fit-tool decoded FIT strings strictly, so a single bad byte raised an error that aborted the entire heart-rate extraction. HR extraction now decodes FIT strings leniently, so the file parses and the heart rate comes through, letting Replace upload a named activity instead of falling back to keeping the watch copy (which showed exercise names as "unknown").