Provides a clean, self-contained argument definition and parsing system. Supports short/long options, defaults, required arguments, value aliases, and summary generation. It imports only internal Argument, Filter, and Summary classes, but the core parsing logic is isolated enough to be extracted into a standalone library for any CLI tool.

Implements the factory pattern to detect the operating system and return the appropriate System implementation (Linux or Windows). Decouples platform-specific terminal operations (dimensions, ANSI support) from the rest of the library. This class is minimal and could be reused independently to provide terminal capabilities from a single factory call.

A simple output buffer that implements WriterInterface. It stores all written output in memory and provides a method to retrieve it. Useful for testing, deferred output, or capturing terminal output without side effects. The implementation is straightforward, has zero internal dependencies (only the interface), and can be extracted and reused in any project needing an in-memory writer.