docs(openspec): propose setup-foundation change

Add OpenSpec change for SPEC Phase 0 — Foundation with proposal,
design, capability specs, and implementation tasks. Populate
openspec/config.yaml with project context and artifact rules.

Co-authored-by: Cursor <cursoragent@cursor.com>

openspec/changes/setup-foundation/specs/design-tokens/spec.md

@@ -0,0 +1,28 @@
+## ADDED Requirements
+
+### Requirement: Design tokens are centralized for the public site
+
+The system SHALL define minimum design tokens in a single source consumed by the public site layout and components. Tokens MUST cover typography families, font scale, spacing, border radius, container width, background/text/border/accent/state colors, shadows, and transition duration/easing.
+
+#### Scenario: Public layout uses shared tokens
+
+- **WHEN** a public page is rendered
+- **THEN** visual properties MUST be derived from the centralized token definitions rather than arbitrary inline values
+
+### Requirement: Public site respects reduced motion preference
+
+The system SHALL honor `prefers-reduced-motion` by disabling or minimizing non-essential animations and transitions on the public site.
+
+#### Scenario: User prefers reduced motion
+
+- **WHEN** a visitor has `prefers-reduced-motion: reduce` enabled
+- **THEN** the public site MUST NOT play non-essential motion effects
+
+### Requirement: Public site meets baseline accessibility contrast
+
+The system SHALL use color combinations on the public site that meet WCAG AA contrast requirements for text and interactive elements defined in the token palette.
+
+#### Scenario: Primary text is readable
+
+- **WHEN** primary body text is rendered on its background color
+- **THEN** the contrast ratio MUST meet WCAG AA minimums