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/lib/utils.ts

@@ -0,0 +1,6 @@
+import { type ClassValue, clsx } from 'clsx'
+import { twMerge } from 'tailwind-merge'
+
+export function cn(...inputs: ClassValue[]) {
+  return twMerge(clsx(inputs))
+}