Motivation

• Provide a small, handover-friendly package that extracts and refactors the multisegment retention model from rm_code so teams can easily compute chromatograms from retention parameters and gradient programs without the full research repo.
• Make the API explicit and typed to reduce onboarding friction and to facilitate regression checks against the legacy implementation.

Description

• Add a new package under chromatogram_handover/ containing a refactored model in src/chromatogram_handover/model.py that exposes GradientProgram, RetentionParameters, Chromatogram, retention_time_and_width, and compute_chromatogram as a clear API.
• Add an I/O helper load_retention_parameters in src/chromatogram_handover/io.py for two-column k0,S files and expose public symbols from __init__.py for minimal import ergonomics.
• Provide packaging metadata in pyproject.toml, a focused README.md with install and minimal usage examples, and a .gitignore to keep artifacts out of the package.
• Add regression tests in chromatogram_handover/tests/test_model.py that compare outputs against the legacy rm_code.retention_model.compute_chromatogram and validate input errors for bad gradient definitions.

Testing

• Ran static bytecode checks with python -m py_compile chromatogram_handover/src/chromatogram_handover/*.py chromatogram_handover/tests/test_model.py, which completed successfully.
• Attempted to run unit tests with pytest chromatogram_handover/tests -q, but test collection was blocked by a missing numpy dependency in the current environment (no numpy installed).
• Attempted to install dependencies with python -m pip install numpy pytest -q, but installation failed due to restricted network/package-index access in this environment, so pytest could not be executed here.

Codex Task