add: docs (#551)

Author: troychaplin

docs/ARCHITECTURE.md

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+# Architecture
+
+This document describes the system architecture, project structure, and build process for the Raven Design System.
+
+## Table of Contents
+
+- [Project Structure](#project-structure)
+- [Build System](#build-system)
+- [Module System](#module-system)
+- [Component Architecture](#component-architecture)
+- [Dependency Management](#dependency-management)
+- [Configuration Files](#configuration-files)
+
+## Project Structure
+
+```
+rds/
+├── lib/                          # Source code
+│   ├── components/               # 51 UI components
+│   │   ├── Alert/
+│   │   │   ├── Alert.tsx         # Component implementation
+│   │   │   ├── Alert.stories.tsx # Storybook stories
+│   │   │   └── styles.css        # Component styles
+│   │   └── ...
+│   ├── layouts/                  # 10 layout components
+│   ├── data/                     # Sample data for stories (26 files)
+│   ├── helpers/                  # Validation schemas, utilities
+│   ├── hooks/                    # Custom React hooks (3 hooks)
+│   ├── styles/                   # Global CSS files
+│   ├── utils/                    # Utility functions and prop classes
+│   ├── docs/                     # Storybook MDX documentation
+│   ├── main.ts                   # Main export barrel file
+│   └── style.css                 # Primary CSS entry point
+│
+├── .storybook/                   # Storybook configuration
+│   ├── main.ts                   # Main config
+│   └── preview.ts                # Preview config
+│
+├── cypress/                      # E2E and component tests
+│   ├── e2e/                      # E2E test files
+│   ├── fixtures/                 # Test fixtures
+│   └── support/                  # Test helpers
+│
+├── public/                       # Static assets
+│   ├── assets/
+│   │   ├── font-awesome/         # Icons
+│   │   └── bg-images/            # Background images
+│   └── sample-imgs/              # Sample images for demos
+│
+├── dist/                         # Build output (generated)
+│   ├── rds.es.js                 # ES module bundle
+│   ├── rds.umd.js                # UMD bundle
+│   ├── main.d.ts                 # TypeScript declarations
+│   └── style.css                 # Compiled CSS
+│
+└── Configuration files
+    ├── vite.config.ts            # Vite/Rollup configuration
+    ├── tailwind.config.ts        # Tailwind CSS configuration
+    ├── tsconfig.json             # TypeScript configuration
+    ├── eslint.config.mjs         # ESLint configuration
+    ├── .prettierrc               # Prettier configuration
+    ├── cypress.config.ts         # Cypress configuration
+    └── package.json              # Dependencies and scripts
+```
+
+## Build System
+
+### Vite + Rollup
+
+The library uses Vite 6.3 with Rollup for production builds.
+
+**Key Configuration** (`vite.config.ts`):
+
+```typescript
+export default defineConfig({
+  plugins: [react(), dts({ rollupTypes: true })],
+  build: {
+    lib: {
+      entry: resolve(__dirname, 'lib/main.ts'),
+      name: 'rds',
+      formats: ['es', 'umd'],
+      fileName: (format) => `rds.${format}.js`,
+    },
+    rollupOptions: {
+      external: [/* all dependencies externalized */],
+      output: {
+        globals: {
+          react: 'React',
+          'react-dom': 'ReactDOM',
+          // ... other globals
+        },
+      },
+    },
+  },
+})
+```
+
+### Build Outputs
+
+| Output | Format | Use Case |
+|--------|--------|----------|
+| `dist/rds.es.js` | ES Modules | Modern bundlers (Vite, webpack 5+) |
+| `dist/rds.umd.js` | UMD | Browser `<script>` tags, older bundlers |
+| `dist/main.d.ts` | TypeScript | Type definitions |
+| `dist/style.css` | CSS | Compiled styles |
+
+### Bundle Size Limits
+
+Enforced via `size-limit` package:
+
+```json
+{
+  "size-limit": [
+    { "path": "dist/rds.es.js", "limit": "200 kB" },
+    { "path": "dist/rds.umd.js", "limit": "200 kB" }
+  ]
+}
+```
+
+### Build Scripts
+
+```bash
+# Full build (lint, format, compile, size check)
+npm run build
+
+# Storybook build
+npm run build:storybook
+
+# Generate asset lists
+npm run create-lists
+```
+
+### CSS Processing
+
+PostCSS pipeline with:
+1. **Tailwind CSS** - Utility-first styles
+2. **PostCSS Nesting** - CSS nesting support
+3. **Autoprefixer** - Browser prefixes
+
+## Module System
+
+### Export Pattern
+
+The library uses a **barrel export pattern** in `lib/main.ts`:
+
+```typescript
+// Components
+export { Alert } from './components/Alert/Alert'
+export { Button } from './components/Button/Button'
+export { Card } from './components/Card/Card'
+// ... 50+ more
+
+// Layouts
+export { Article } from './layouts/Article/Article'
+export { Column } from './layouts/Column/Column'
+// ... more layouts
+
+// Utilities
+export * as utils from './utils/propClasses'
+export { iconNames } from '../public/assets/font-awesome/icon-list.js'
+export { bgImageNames } from '../public/assets/bg-images/bg-image-list.js'
+
+// CSS (side effect)
+import './style.css'
+```
+
+### Package Exports
+
+```json
+{
+  "exports": {
+    ".": {
+      "types": "./dist/main.d.ts",
+      "import": "./dist/rds.es.js",
+      "require": "./dist/rds.umd.js"
+    },
+    "./dist/style.css": "./dist/style.css"
+  }
+}
+```
+
+### External Dependencies
+
+All dependencies are externalized to avoid bundling:
+
+```typescript
+external: [
+  'react',
+  'react-dom',
+  'formik',
+  'yup',
+  'date-fns',
+  'react-select',
+  'react-player',
+  'dompurify',
+  '@react-google-maps/api',
+  // ... etc
+]
+```
+
+## Component Architecture
+
+### Standard Component Structure
+
+```
+ComponentName/
+├── ComponentName.tsx         # Main component
+├── ComponentName.stories.tsx # Storybook stories
+├── styles.css                # Component-scoped styles
+└── [SubComponents.tsx]       # Optional sub-components
+```
+
+### Composite Component Pattern
+
+Complex components use `Object.assign` for sub-component attachment:
+
+```typescript
+// Card.tsx
+const CardWrapper = ({ children, ...props }) => (
+  <div {...props}>{children}</div>
+)
+
+export const Card = Object.assign(CardWrapper, {
+  Figure: CardFigure,
+  Header: CardHeader,
+  Body: CardBody,
+  Content: CardContent,
+  Footer: CardFooter,
+  // ... more subcomponents
+})
+```
+
+**Usage:**
+```tsx
+<Card>
+  <Card.Figure src="/image.jpg" />
+  <Card.Body>
+    <Card.Header title="Card Title" />
+    <Card.Content>Content here</Card.Content>
+  </Card.Body>
+</Card>
+```
+
+### TypeScript Patterns
+
+**Props Interface Pattern:**
+```typescript
+export interface ButtonProps extends React.ComponentPropsWithoutRef<'button'> {
+  color?: 'red' | 'grey' | 'dark-grey' | 'black' | 'white'
+  isSmall?: boolean
+  isFull?: boolean
+  isDisabled?: boolean
+}
+```
+
+**Discriminated Union Pattern:**
+```typescript
+// Button with title
+interface ButtonTitleProps extends BaseButtonProps {
+  title: string
+  children?: never
+}
+
+// Button with children
+interface ButtonChildrenProps extends BaseButtonProps {
+  children: React.ReactNode
+  title?: never
+}
+
+type ButtonProps = ButtonTitleProps | ButtonChildrenProps
+```
+
+### Context Providers
+
+**LinkProvider** for customizable link components:
+
+```typescript
+// LinkContext.tsx
+export const LinkContext = createContext<React.ElementType>('a')
+export const useLinkContext = () => useContext(LinkContext)
+
+// Usage in component
+const Link = useLinkContext()
+return <Link href={url}>{children}</Link>
+
+// App-level customization
+import { Link } from 'next/link'
+<LinkProvider value={Link}>
+  <App />
+</LinkProvider>
+```
+
+## Dependency Management
+
+### Peer Dependencies
+
+```json
+{
+  "peerDependencies": {
+    "react": "^19.2.0",
+    "react-dom": "^19.2.0"
+  }
+}
+```
+
+### Key Runtime Dependencies
+
+| Package | Version | Purpose |
+|---------|---------|---------|
+| `formik` | 2.4.9 | Form state management |
+| `yup` | 1.7.1 | Schema validation |
+| `date-fns` | 4.1.0 | Date utilities |
+| `react-select` | 5.10.2 | Enhanced select dropdown |
+| `react-player` | 3.4.0 | Video player |
+| `dompurify` | 3.3.1 | HTML sanitization |
+| `@react-google-maps/api` | 2.20.8 | Google Maps |
+
+### Styling Dependencies
+
+| Package | Purpose |
+|---------|---------|
+| `tailwindcss` | Utility CSS framework |
+| `rds-tailwind-theme` | Carleton custom theme preset |
+| `@tailwindcss/forms` | Form element styles |
+| `@tailwindcss/typography` | Prose styles |
+| `@tailwindcss/aspect-ratio` | Aspect ratio utilities |
+| `@tailwindcss/container-queries` | Container queries |
+
+## Configuration Files
+
+### TypeScript (`tsconfig.json`)
+
+```json
+{
+  "compilerOptions": {
+    "target": "ES2020",
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "jsx": "react-jsx",
+    "strict": true,
+    "noImplicitAny": true,
+    "strictNullChecks": true,
+    "skipLibCheck": true,
+    "noEmit": true
+  }
+}
+```
+
+### Tailwind (`tailwind.config.ts`)
+
+```typescript
+export default {
+  presets: [require('rds-tailwind-theme')],
+  content: ['./lib/**/*.{tsx,ts,jsx,js}'],
+  darkMode: 'selector', // .dark class-based
+  // Theme extensions...
+}
+```
+
+### ESLint (`eslint.config.mjs`)
+
+- Flat config format (ESLint 9+)
+- TypeScript support
+- React/React Hooks rules
+- Prettier integration
+- Storybook plugin
+- Cypress plugin
+
+### Prettier (`.prettierrc`)
+
+```json
+{
+  "trailingComma": "all",
+  "tabWidth": 2,
+  "semi": false,
+  "singleQuote": true,
+  "printWidth": 120,
+  "bracketSpacing": true
+}
+```
+
+## Areas for Improvement
+
+### Current Issues
+
+1. **Large bundle size** - CSS includes unused Tailwind utilities
+2. **No tree-shaking** - All components bundled together
+3. **Tight Tailwind coupling** - Hard to customize without Tailwind knowledge
+4. **Limited CSS isolation** - Global styles can leak
+
+### Planned Improvements
+
+1. **SCSS Migration** - Move to CSS modules for better isolation
+2. **Component-level exports** - Enable tree-shaking
+3. **CSS extraction** - Separate critical and non-critical CSS
+4. **Better TypeScript** - Stricter types for Gutenberg integration
+
+See [MIGRATION.md](./MIGRATION.md) for the Tailwind to SCSS migration plan.