Reverse engineer Boxsim MyIni2CK container, add bpj2ini decoder

Format: 8-byte magic, XOR layer (table-shuffled 3-LCG PRNG, seeds 123/456),
custom LZ+Huffman codec (A2F). Decompression runs the original ExpandA2F
code from Boxsim.exe under Unicorn. Decodes .bpj and .bch files.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,6 @@
+*.zip
+boxsim_dl/
+brute
+
+.claude/
+__pycache__/