Moved the `ChunkerFixed` implementation from `chunker` to a new `fixed` module for better modularity. Updated imports and type hints.
Removed now empty chunkers.chunker module.
Moved `buzhash` implementation from `chunker` to a new `buzhash` module for better separation of concerns. Updated imports, adjusted `setup.py` and build configuration accordingly. Removed deprecated `Chunker` definitions from `chunker.pyi`.
Extracted the `reader` logic from `chunker` into a dedicated `reader` module to improve modularity and maintainability. Updated imports, references, and build configurations accordingly.