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>

.storybook/main.ts

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+import type { StorybookConfig } from '@storybook/react-vite';
+
+const config: StorybookConfig = {
+  "stories": [
+    "../src/**/*.mdx",
+    "../src/**/*.stories.@(js|jsx|mjs|ts|tsx)"
+  ],
+  "addons": [
+    "@chromatic-com/storybook",
+    "@storybook/addon-vitest",
+    "@storybook/addon-a11y",
+    "@storybook/addon-docs",
+    "@storybook/addon-mcp"
+  ],
+  "framework": "@storybook/react-vite"
+};
+export default config;

.storybook/preview.tsx

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+import type { Preview } from '@storybook/react-vite'
+import '../src/styles/global.css'
+
+const preview: Preview = {
+  parameters: {
+    controls: {
+      matchers: {
+       color: /(background|color)$/i,
+       date: /Date$/i,
+      },
+    },
+
+    a11y: {
+      // 'todo' - show a11y violations in the test UI only
+      // 'error' - fail CI on a11y violations
+      // 'off' - skip a11y checks entirely
+      test: 'todo'
+    }
+  },
+};
+
+export default preview;