the duration-agreement check used abs() drift, so a file running LONGER than the metadata
(a remaster with a longer outro, an extended cut) was rejected the same as a truncated one —
e.g. A-Ha 'Take on Me' remaster at 228.5s vs 225.0s expected, quarantined for +3.5s.
but a longer file is the OPPOSITE of truncated. make the auto tolerance asymmetric: keep the
tight 3s/5s bound for SHORTER files (the truncation case the check exists for), allow up to
15s in the LONGER direction for version/master differences. a wrong song still trips it (off
by far more than 15s), and a user-pinned tolerance is honoured symmetrically. direction-aware
rejection message too. 4 new tests; 274 integrity/import tests green.
