Initial scaffold: React 19 + Vite + TypeScript + Tailwind CSS v4 + Storybook 10

Design system and component library for the Research Synthesiser. Includes:
- Tailwind CSS v4 with @theme-based design tokens from the existing synthesiser
- Storybook 10.4 with MCP, a11y, docs, and vitest addons
- ESLint + Prettier with Tailwind class sorting
- Button component as pipeline validation
- CLAUDE.md with project principles and conventions
- ARCHITECTURE.md as living architecture document
- Penpot and Storybook MCP server configuration

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/tokens/tokens.css

@@ -0,0 +1,37 @@
+@theme {
+  /* Surface colors */
+  --color-bg: #f5f6f8;
+  --color-surface: #ffffff;
+  --color-border: #e2e5ea;
+
+  /* Text colors */
+  --color-text: #1a1d23;
+  --color-text-secondary: #5f6672;
+
+  /* Primary */
+  --color-primary: #2563eb;
+  --color-primary-hover: #1d4ed8;
+  --color-primary-light: #eff4ff;
+
+  /* Semantic: Success */
+  --color-success: #16a34a;
+  --color-success-bg: #dcfce7;
+
+  /* Semantic: Warning */
+  --color-warning: #d97706;
+  --color-warning-bg: #fef9c3;
+
+  /* Semantic: Error */
+  --color-error: #dc2626;
+  --color-error-bg: #fee2e2;
+
+  /* Radius */
+  --radius-sm: 4px;
+  --radius-default: 6px;
+  --radius-lg: 10px;
+  --radius-full: 9999px;
+
+  /* Shadows */
+  --shadow-default: 0 1px 3px rgba(0, 0, 0, 0.08);
+  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
+}