Add CLI support

Add `cli` module so it can be easily executed from command line

Start by locating the Rust crate's public entry points and existing build or packaging configuration; the issue names no files or tests. Determine the command-line behavior required for the CLI module and verify that it can execute the library from a shell. Done means the command-line interface is usable, though the issue does not define its commands or acceptance criteria.

Written by the indexing model from the issue text.