Create / Extract DESIGN.md

DESIGN.md = YAML design tokens (machine-readable) + 8 ordered markdown sections (human-readable rationale). Two modes: extract from existing source code, create from design intent.

MANDATORY READ before any token work (Phase 3+): references/design-md-spec.md — Do NOT load during Phases 1 and 2.

Phase 1 — Detect Mode

Extract — frontend source exists. Signals: package.json, tailwind.config.js, CSS/SCSS files, component directories with repeated styles.

Create — no extractable source. User provides brand brief, palette, adjectives, or aesthetic description.

Ambiguous → ask: "Extract design tokens from existing source code, or create from a design brief?"

If an existing DESIGN.md is present → ask: "Update existing file or replace it?"

Exit criterion: mode is unambiguous and any existing file decision is made.