Strava originals with absolute Unix timestamps stored as elapsed-second
offsets produce a t_max of ~1.6 billion. compute_mmp and compute_best_efforts
both create dense 1Hz arrays via range(t_min, t_max+1), which for a 1.6B
span allocates 44+ GB and OOM-kills the process. Add a >1-week sanity
check and return None early for corrupt streams.
Root cause: old Strava activities (seen from 1970-epoch start_date)
where the time stream contains absolute Unix timestamps instead of
elapsed seconds.
Davide Scaini