The original UC2 Pro handles archives differently based on versionMadeBy:
300 causes multi-file listing to fail, while 203 (the original's own
version) works correctly. Also write method=compression_level in file
COMPRESS records instead of hardcoded 1.
Combined with the earlier csize=0 and default-tree fixes, single-file
UC2 v3 archives are now fully backward compatible with the original
UC2 Pro (listing + extraction verified). Multi-file archives can be
listed but extraction still hangs — under investigation.
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