Fixes#895 — https://github.com/Nezreka/SoulSync/issues/895
HiFi (Tidal via hifi-api) sometimes serves a PREVIEW HLS manifest — only ~30s of
segments — for a full-length track. SoulSync downloaded exactly what the manifest
contained, and the only validation was a 100KB size floor (a 30s lossless preview is
~3-4MB, so it passed as 'complete') → a junk file that shows full length but plays ~30s.
Add two duration guards, both keyed off the track's real length (from get_track_info):
- Pre-download: sum the manifest's #EXTINF segment durations; if far short of the
expected track length, it's a preview → skip that tier, fall through to the next
source without wasting the download. (The parser discarded #EXTINF before.)
- Post-download: probe the finished file's real length (mutagen) and reject if short —
backs up legacy/direct (no-EXTINF) downloads and catches any truncation.
Conservative: unknown/zero durations never reject. Pure sum_hls_segment_seconds /
is_short_audio helpers with seam tests.
