docs: comprehensive documentation update

Update README with detailed project overview, features, installation, and usage. Add AGENTS.md developer guide, CONTRIBUTING.md guidelines, MIT LICENSE file, and fix CI workflow configuration.

CONTRIBUTING.md

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+# Contributing to d@n tech Portfolio
+
+Thank you for your interest in contributing to this web development portfolio project! This document provides guidelines for contributing.
+
+## How to Contribute
+
+1. **Fork the Repository** - Click the "Fork" button on GitHub to create your own copy.
+2. **Clone Your Fork** - `git clone https://github.com/YOUR-USERNAME/webdev-site.git`
+3. **Create a Feature Branch** - `git checkout -b feature/your-feature-name`
+4. **Make Your Changes** - Follow the code style guidelines below.
+5. **Test Your Changes** - Ensure the site builds and works across browsers.
+6. **Commit Your Changes** - `git commit -m "Add your descriptive message"`
+7. **Push to Your Fork** - `git push origin feature/your-feature-name`
+8. **Open a Pull Request** - Navigate to the original repository and open a PR.
+
+## Code Style Guidelines
+
+Please adhere to the existing code style to maintain consistency:
+
+### JavaScript
+- Use ES6+ modules with `type="module"` in HTML
+- Prefer `const` over `let`; avoid `var`
+- Arrow functions for callbacks; named functions for top-level declarations
+- CamelCase for variables/functions; PascalCase for classes
+- Check element existence before DOM manipulation
+- Use section headers: `// ===== SECTION NAME =====`
+
+### CSS
+- Use CSS Custom Properties defined in `:root` with semantic names
+- CSS Nesting with `&` for nested selectors (modern browsers)
+- Mobile-first media queries with `min-width`
+- Support `prefers-color-scheme: dark` with variable overrides
+- Kebab-case for class names
+
+### HTML
+- Semantic HTML5 elements (`<header>`, `<main>`, `<section>`)
+- Include ARIA attributes where needed; proper heading hierarchy
+- Use Bootstrap classes alongside custom styles
+- `data-*` attributes for JavaScript hooks
+- Lazy loading for images; defer non-critical scripts
+
+## Testing
+
+Before submitting a pull request, please verify:
+
+1. **Build Success** - Run `npm run build` to ensure no errors
+2. **Cross-Browser Compatibility** - Test in at least Firefox and Chrome
+3. **Responsive Design** - Check mobile (375px) and desktop (1200px) views
+4. **No Console Errors** - Open browser developer tools and ensure no errors
+5. **Lighthouse Audit** - Run `npx lighthouse http://localhost:4173` for performance, accessibility, SEO, and best practices
+
+## Reporting Issues
+
+When reporting issues, please include:
+
+- Steps to reproduce the issue
+- Expected vs. actual behavior
+- Browser and operating system information
+- Screenshots if applicable
+
+## Questions?
+
+If you have questions, please open an issue or contact the maintainer via the portfolio site: [dev.dustin.coffee](https://dev.dustin.coffee/)
+
+---
+
+*Thank you for contributing!*