Transforms loose ideas or refined concepts into structured PRDs that capture the what, who, and why — problem, target users, goals, non-goals, and testable acceptance criteria — while deliberately deferring the how (architecture, data models, APIs, delivery phasing) to the planning phase. Works through a progressive interview, light de-risking of risky assumptions, and optional codebase exploration. Use when asked to "write a PRD", "create a PRD", "design a feature", "flesh out this idea", "turn this into a spec", "product requirements", "spec this out", or /prd-designer. Outputs a markdown PRD at docs/prds/{name}.md. Optionally creates a GitHub issue via gh CLI. Dependencies: gh CLI (optional, for issue creation).