[Phase 1] Set up Astro + Starlight project structure

[afucher]

Initialize the Astro + Starlight project in website/ directory with all necessary configuration files and dependencies.

Deliverable

A fully functional Astro + Starlight project that builds successfully locally and produces website/dist/ output.

Acceptance Criteria

• website/ directory created with package.json (separate from library)
• astro.config.mjs configured with Starlight integration
  • Site URL: https://astrodraw.github.io (no base path)
  • Title: AstroChart
  • Sidebar structure defined for the main sections
• tsconfig.json in website/ configured for TypeScript
• src/components/ directory created with skeleton components
  • ChartDemo.astro (empty, will implement in next task)
  • SinceBadge.astro (simple version badge component)
• src/content/docs/ directory created with placeholder index.mdx
• public/ directory created with placeholder astrochart.js
• All dependencies installed: astro, @astrojs/starlight, @astrojs/sitemap, sharp
• npm run build produces output in website/dist/
• npm run dev starts dev server at http://localhost:4321
• No TypeScript errors or build warnings

Related Plan Section

docs-plan.md §2 (Technology Stack), §3 (Repository Structure), §4.2 (Sidebar)