Style-neutral procedure for deriving a project's own design system. Walks a project from domain evidence to design principles, recorded design decisions, and a 3-layer token architecture (Primitive → Semantic ← [data-theme] → Component). Use when: establishing design principles for a new project, creating a project design guide (docs/design.md), setting up a design token system, or reviewing a project's design foundation completeness. Does NOT prescribe colors, fonts, spacing, or trends — those are project decisions.
