Root cause: the original UC2 Pro expects csize=0 in the cdir COMPRESS
record (it ignores the field entirely). UC2 v3 was writing the actual
compressed size, which confused the original's archive reader.
Additional changes:
- Use default Huffman tree for all blocks (ensures tree encoding compat)
- Write method=compression_level in cdir COMPRESS (was hardcoded to 1)
- Add tests/scripts/bitdump.py for bit-level bitstream analysis
Single-file UC2 v3 archives are now fully readable by the original UC2
Pro (listing and extraction verified in DOSBox-X). Multi-file archives
still hang — the cdir bitstream decodes correctly in our Python analyzer
but fails in the original's ASM decompressor kernel. Investigation
continues; the bitdump.py tool enables targeted comparison.
c736b19bae