- Implemented aes_128_decrypt with CBC mode + PKCS#7 padding
- Implemented derive_aes_128_object_key with 'sAlT' suffix
- Implemented is_identity_filter for crypt filter handling
- All 11 unit tests passing
- Integration work deferred to coordinator bead pdftract-1z0qt
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
