media3 1.11.0 builds the Matroska seek map while parsing Cues, which for
files whose Tracks element follows the Clusters is before any track is
known — the map permanently reports unseekable and ExoPlayer coerces
every seek to t=0, snapping playback to the start. Route seeks through
TrackAwareSeekMap's per-track cue lookups using the track IDs observed
on the extractor output.
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