feat(dev): add claude.md

Author: hwindo

CLAUDE.md

@@ -0,0 +1,47 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Development Commands
+
+**Local Development:**
+```bash
+bundle install          # Install Ruby dependencies
+bundle exec jekyll serve # Start local server at http://127.0.0.1:4000
+```
+
+**Build:**
+```bash
+bundle exec jekyll build --baseurl ""  # Build site to _site directory
+```
+
+## Architecture Overview
+
+This is a Jekyll-based portfolio website hosted on GitHub Pages. The site showcases projects, blog posts, and includes interactive playground components.
+
+**Key Structure:**
+- `_config.yaml` - Main Jekyll configuration
+- `_data/project_list.yml` - Central project database with metadata, descriptions, and links
+- `_layouts/` - Page templates (default, frontpage, post, etc.)
+- `_includes/` - Reusable components (header, nav, footer, project-list)
+- `_sass/` - Modular SCSS stylesheets imported via `css/styles.scss`
+- `_playground/` - Interactive demo components with their own collection
+- `_posts/` - Blog articles in markdown format
+
+**Frontend Architecture:**
+- Vanilla JavaScript with ES6 modules in `assets/js/`
+- Component-based JS (logo animation, screen loader)
+- SCSS with BEM-style organization
+- Service Worker for offline functionality
+- Progressive Web App features (manifest.json, icons)
+
+**Content Management:**
+- Projects are managed via YAML data file rather than individual markdown files
+- Each project includes metadata (role, year, tags), descriptions, and multiple URL types
+- Collections system used for playground demonstrations
+- Blog posts follow Jekyll's standard `_posts/` structure
+
+**Deployment:**
+- GitHub Actions workflow deploys to GitHub Pages automatically on push to main
+- Ruby 3.1 with Ubuntu 22.04 build environment
+- Site builds with production JEKYLL_ENV