Stack Add

Systematically add a new framework or stack to the CLI following the `adding-stacks` skill.

This command will guide you through:
- Creating a reference project FIRST
- Understanding the framework architecture completely
- Identifying ALL dependencies and their exact versions
- Creating complete template files
- Testing generation in both single and turborepo modes
- Handling special file naming conventions (like triple underscore)

**Core principle:** Understand-first, not copy-first!