Add React Native skill

[yuvrajangadsingh]

Adds a react-native skill that converts Stitch HTML designs into React Native components with StyleSheet.

Closes #41, relates to #19.

What it does

• Maps HTML elements to React Native primitives (View, Text, Pressable, Image, FlatList, etc.)
• Converts CSS/Tailwind to StyleSheet.create() with theme token references
• Handles platform-specific code (Platform.select() for shadows, SafeAreaView for notch handling)
• Uses Atomic Design for component organization (atoms/molecules/organisms)
• Includes accessibility (accessibilityLabel, accessibilityRole, accessibilityState)
• Decouples data into mockData.ts, logic into custom hooks
• Provides AST validation that catches HTML elements, missing Props interfaces, and hardcoded hex values

Skill structure

skills/react-native/
├── SKILL.md                              — Core instructions & workflow
├── README.md                             — Install & usage
├── package.json                          — Validator dependencies
├── scripts/fetch-stitch.sh               — Stitch asset downloader
├── scripts/validate.js                   — AST validator (Props, hex, HTML element checks)
├── resources/architecture-checklist.md   — Quality gate checklist
├── resources/component-template.tsx      — Starter template
└── examples/gold-standard-card.tsx       — Reference implementation

Modeled after the existing react-components skill, adapted for React Native's different primitives, styling system, and platform constraints.

[davideast]

Another one! Thank you @yuvrajangadsingh! I'm finding time to review.