refactor: make bbl_format module public for crate users

Export bbl_format module publicly so crate users can access:
- BBLDataStream for parsing binary data
- Encoding/predictor constants (ENCODING_*, PREDICT_*)
- parse_frame_data for frame parsing
- sign_extend_14bit for 14-bit encoding

This enables external crates and the CLI binary to use the same
stream and parsing implementation.

Addresses Issue #9: Refactor CLI to use crate library functions

Author: nerdCopter

src/lib.rs

@@ -16,7 +16,7 @@
 //! ```
 
 // Module declarations
-mod bbl_format;
+pub mod bbl_format;
 pub mod conversion;
 pub mod error;
 pub mod export;