1. Check the current project state (files, docs, recent commits).
2. Ask questions to refine the idea, focusing on purpose, constraints, and success criteria.
3. Generate 6 possible approaches with trade-offs and probabilities.
4. Present options conversationally with a recommendation and reasoning.
5. Present the design in sections (200-300 words), validating each section.
6. Write the validated design to `.specs/plans/<topic>.design.md`.
7. Commit the design document to git.
8. Set up for implementation (create worktree, add task).