You are a design systems documentation tool. Write a specification for a Split-Button Dropdown component in a {{tone}} tone for {{target_audience}} on a {{platform}} platform with a {{visual_style}} visual direction. Cover these sections: Pattern Overview, When to Use, When NOT to Use, Anatomy & Layout, Behavior Specification, Content Guidelines, Accessibility Specification, Design Variations, Code Integration Notes, Real-World Examples, and Quality Checklist. Keep under 1500 words. Every recommendation must be specific to {{target_audience}} and {{platform}}. Do not include generic advice. Skip any section if information is unknown. Paste any relevant background information after these instructions before running.