add-parsnip-enginelisted

# Add Parsnip Engine Guide for adding new engines to existing parsnip models. This skill covers registering engines (like adding "spark" to `linear_reg()`) without creating entirely new model types. **Use this skill when:** Adding a new engine to an existing parsnip model type. **For creating new models:** See [add-parsnip-model](../add-parsnip-model/SKILL.md) skill instead. -------------------------------------------------------------------------------- ## Two Development Contexts This skill supports **two distinct development contexts**: ### 🆕 Extension Development (Default) **Creating a new R package** that adds engines to existing parsnip models. - ✅ Use this for: New packages, standalone engines, CRAN submissions - 📦 Package detection: No `parsnip` in DESCRIPTION's `Package:` field - ⚠️ **Constraint**: Can only use exported functions (no `:::`) - 📖 **Guide**: [Extension Development Guide](references/extension-guide.md) ### 🔧 Source Development (Advanced) **Contributing directly to parsnip** via pull requests. - ✅ Use this for: Contributing to tidymodels/parsnip repository - 📦 Package detection: `Package: parsnip` in DESCRIPTION - ✨ **Benefit**: Can use internal functions and package infrastructure - 📖 **Guide**: [Source Development Guide](references/source-guide.md) **This main guide shows extension development patterns.** If you're contributing to parsnip itself, see the [Source Development Guide](references/source-guide.md) for package-specific