Shared Python package used by all engineering skill scripts in this repository (JSON envelope, license-notification helper, dimensionless numbers, fluids/heat-transfer wrappers, VLE/separations/reactor helpers, compositional data, causal DAG, time-series, separator/valve helpers). Use when authoring a new skill or refactoring an existing one that needs shared utilities. Don't use as a user-facing skill — it has no CLI and no engineering output of its own.
