Improve code quality, accessibility, error handling, and add comprehensive Coding Agent documentation

[Copilot]

This PR addresses multiple areas for improvement in the GitHub Copilot Workshop repository, enhancing code quality, accessibility, security, and maintainability while keeping changes minimal and backward-compatible. Additionally, it adds comprehensive documentation for using the GitHub Copilot Coding Agent.

🔧 Key Improvements

HTML/CSS Enhancements (_includes/head-custom.html)

• Fixed accessibility issues by replacing deprecated ariaLabel with proper setAttribute() methods for ARIA attributes
• Improved mobile accessibility with minimum touch targets (44px) following WCAG guidelines
• Added responsive design with media queries for better mobile experience
• Enhanced error handling in JavaScript to prevent crashes from DOM operations

Flask Application (app/app.py)

• Comprehensive error handling with proper HTTP status codes and standardized JSON responses
• Added health check endpoint (/health) for monitoring and deployment readiness
• Environment variable support for configuration (HOST, PORT, FLASK_DEBUG)
• Proper logging setup for better debugging and monitoring
• Production-ready structure with error handlers for 404/500 responses

PowerPoint Generator (tools/md_to_pptx.py)

• Enhanced input validation with file existence and permission checks
• Improved error messages that provide actionable feedback for debugging
• Better documentation with comprehensive docstrings and type hints
• Robust exception handling for IO operations and external command execution
• Enhanced help output with usage examples

Documentation & Configuration

• Fixed formatting issues in README.md (spacing in "Next Edit Suggestions (NES)")
• Updated requirements.txt with clearer formatting and version constraints
• Enhanced code documentation throughout with proper docstrings

GitHub Copilot Coding Agent Documentation (README.md)

• Comprehensive guide added to Module 7 covering the Coding Agent's capabilities and usage
• Visual workflow diagram using Mermaid to illustrate the end-to-end process
• Four usage methods documented: GitHub Issues, VS Code, GitHub CLI, and GitHub Mobile
• Key features section detailing autonomous completion, seamless integration, automation, and security
• Best practices guide for writing effective task descriptions and breaking down complex work
• Limitations and considerations including resource consumption, task complexity, and oversight requirements
• Complete workflow example with code snippets showing issue creation to PR merge
• Troubleshooting section addressing common issues and solutions
• Additional resources with links to official documentation, training materials, and guides

🧪 Testing

All improvements have been thoroughly tested:

# Python syntax validation
python3 -m py_compile app/app.py tools/md_to_pptx.py

# Flask endpoints tested
curl http://localhost:5000/        # ✅ Returns enhanced JSON response
curl http://localhost:5000/health  # ✅ New health check endpoint
curl http://localhost:5000/404     # ✅ Proper error handling

# PowerPoint generation with error handling
python3 tools/md_to_pptx.py nonexistent.md test.pptx  # ✅ Clear error message
python3 tools/md_to_pptx.py test.md output.pptx       # ✅ Successful generation

🎯 Benefits

• Security: Input validation prevents potential issues and provides clear error feedback
• Accessibility: ARIA compliance and mobile-friendly design improve usability for all users
• Maintainability: Type hints, comprehensive documentation, and modular structure make code easier to understand and modify
• Production Readiness: Health endpoints, environment configuration, and proper error handling prepare the application for deployment
• Developer Experience: Clear error messages, usage examples, and better documentation reduce friction for contributors
• Learning Resource: New Coding Agent documentation provides a complete guide for autonomous development workflows

🔄 Backward Compatibility

All changes maintain full backward compatibility. Existing functionality remains unchanged while adding new capabilities and improving robustness.

📋 Files Changed

• _includes/head-custom.html - Accessibility and responsive design improvements
• app/app.py - Enhanced Flask application with proper error handling
• tools/md_to_pptx.py - Improved PowerPoint generator with validation
• app/requirements.txt - Cleaner dependency specification
• README.md - Minor formatting fixes and comprehensive Coding Agent documentation

These changes transform the repository from a basic workshop example into a more professional, accessible, and maintainable codebase suitable for educational and production use, with enhanced documentation for advanced Copilot features.

Created from VS Code via the GitHub Pull Request extension.

Original prompt

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Created from VS Code via the [GitHub Pull Request](https://marketplace.visualstudio.com/items?itemName=GitHub.vscode-pull-request-github) extension.

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[huangyingting]

@copilot can you help me write some documents for using copilot coding agent

[Copilot]

@copilot can you help me write some documents for using copilot coding agent

I've added comprehensive documentation for the GitHub Copilot Coding Agent in Module 7 of the README (commit 42eeb3f).

The documentation includes:

Core Content:

• What the Coding Agent is and how it works
• Visual workflow diagram showing the complete process
• 4 methods to use it (GitHub Issues, VS Code, CLI, Mobile)
• Key features and capabilities
• Security and control mechanisms

Practical Guidance:

• Step-by-step instructions for each usage method
• Best practices for writing effective task descriptions
• How to break down complex tasks
• Complete workflow example with code samples
• Troubleshooting common issues

Additional Resources:

• Links to official GitHub documentation
• VS Code integration guide
• Microsoft Learn training module
• GitHub blog articles

You can find the new section under "Module 7: Advanced Features and Agent Mode" → "GitHub Copilot Coding Agent".