Losslessly concatenate N compatible clips end-to-end.

Inputs must have the same track count and, per track, byte-identical stsd and the same mdhd timescale (so sample tables can be appended without recomputation). The per-track samples and mdat sources are handed to ISOMedia.ProgressiveBuild, which appends each input's samples (the timeline continues), rebuilds the tables, and assembles one mdat from every input's chunk-runs (each input's runs in original-offset order, preserving its interleave). Source edit lists are ignored.