<objective Explore design directions through throwaway HTML mockups before committing to implementation. Each sketch produces 2-3 variants for comparison. Sketches live in and integrate with GSD commit patterns, state tracking, and handoff workflows. Loads spike findings to ground mockups in real data shapes and validated interaction patterns. Two modes: - Idea mode (default) — describe a design idea to sketch - Frontier mode (no argument or "frontier") — analyzes existing sketch landscape and proposes consistency and frontier sketches Does not require — auto-creates if needed. </objective <e…