Make ready agent cog pip-installable via maturin bin bindings

[MFA-X-AI]

This PR packages the ready Rust binary as a pip-installable wheel using maturin's bindings = "bin" mode. Users can pip install ready-agent (once it's up on pypi) to get the CLI without needing a Rust toolchain.

• Includes a GitHub Actions workflow that runs Rust and Python tests on push/PR, builds wheels for Linux/macOS/Windows (x86_64 + aarch64), and publishes to PyPI on release
• This ships the CLI only - a future iteration can add PyO3 bindings to expose the Rust internals as a Python library API (parse_plan, validate_plan, PlanInterpreter, etc.), similar to how pydantic wraps pydantic-core,