Add CLAUDE.md and update README with badges

- Add CLAUDE.md with AI assistant instructions
- Emphasize 100% test coverage requirement
- Add test status, coverage, and license badges to README
- Update npm installation instructions

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: super3

CLAUDE.md

@@ -0,0 +1,85 @@
+# CLAUDE.md - AI Assistant Instructions
+
+## Important Rules
+
+1. **Test Coverage**: Please run test/coverage before and after any work. Coverage needs to be 100% for a task to be complete.
+   ```bash
+   npm run test:coverage
+   ```
+
+2. **No Commits Without Permission**: Don't commit or push code unless I explicitly tell you to.
+
+3. **Code Quality Standards**:
+   - Maintain 100% test coverage at all times
+   - Follow existing code style and patterns
+   - Use CommonJS modules (not ES6 modules) for compatibility
+   - Keep the zero-dependency philosophy
+
+## Project Structure
+
+```
+mdtail.dev/
+├── lib/
+│   ├── mdtail.js        # Main application class
+│   ├── display.js       # Terminal display logic
+│   ├── fileManager.js   # File operations and watching
+│   └── errors.js        # Custom error classes
+├── test/
+│   ├── mdtail.test.js              # Core unit tests
+│   ├── mdtail.integration.test.js  # Integration tests
+│   ├── mdtail.edge.test.js         # Edge cases
+│   ├── display.test.js             # Display module tests
+│   ├── fileManager.test.js         # File manager tests
+│   └── errors.test.js              # Error classes tests
+├── index.js              # CLI entry point
+├── index.d.ts            # TypeScript definitions
+└── package.json
+
+```
+
+## Testing Commands
+
+```bash
+npm test                  # Run all tests
+npm run test:watch        # Run tests in watch mode
+npm run test:coverage     # Run tests with coverage report
+```
+
+## Common Tasks
+
+### Adding New Features
+1. Run tests first to ensure 100% coverage: `npm run test:coverage`
+2. Implement the feature
+3. Add comprehensive tests for the new feature
+4. Run tests again to ensure 100% coverage is maintained
+5. Do NOT commit unless explicitly asked
+
+### Refactoring
+1. Run tests first to ensure 100% coverage
+2. Make refactoring changes
+3. Ensure all tests still pass
+4. Verify 100% coverage is maintained
+5. Do NOT commit unless explicitly asked
+
+### Bug Fixes
+1. Add a failing test that reproduces the bug
+2. Fix the bug
+3. Ensure the test now passes
+4. Verify 100% coverage is maintained
+5. Do NOT commit unless explicitly asked
+
+## Key Implementation Details
+
+- **File Watching**: Uses `fs.watchFile` with 100ms polling interval
+- **Terminal Features**: Graceful degradation for non-TTY environments
+- **Error Handling**: Custom error classes with helpful suggestions
+- **Display**: ANSI escape codes with fallbacks for limited terminals
+- **Navigation**: Arrow keys for multi-file tab switching
+
+## NPM Publishing
+
+The package is published as `mdtail` on npm. When preparing releases:
+1. Ensure all tests pass with 100% coverage
+2. Update version in package.json
+3. Test the package locally with `npm pack`
+4. Only publish after explicit approval

README.md

@@ -1,5 +1,10 @@
 # mdtail.dev
 
+[![npm version](https://badge.fury.io/js/mdtail.svg)](https://www.npmjs.com/package/mdtail)
+[![Test Status](https://img.shields.io/github/actions/workflow/status/super3/mdtail.dev/ci.yml?branch=main&label=tests)](https://github.com/super3/mdtail.dev/actions/workflows/ci.yml)
+[![Coverage Status](https://coveralls.io/repos/github/super3/mdtail.dev/badge.svg?branch=main)](https://coveralls.io/github/super3/mdtail.dev?branch=main)
+[![License](https://img.shields.io/badge/license-MIT-blue.svg?label=license)](https://github.com/super3/mdtail.dev/blob/main/LICENSE)
+
 A simple terminal app that displays and live-refreshes markdown files.
 
 ## Features
@@ -14,25 +19,26 @@ A simple terminal app that displays and live-refreshes markdown files.
 
 ## Installation
 
+### npm (Recommended)
+```bash
+npm install -g mdtail
+```
+
+### From Source
 ```bash
 git clone https://github.com/super3/mdtail.dev.git && cd mdtail.dev
 npm install
+npm link                           # Install mdtail command globally
 ```
 
 ## Usage
 
-### Local
 ```bash
-npm start                          # Watch TODO.md (default)
-```
-
-### Global Installation
-```bash
-npm link                           # Install mdtail command globally
-mdtail                             # Watch TODO.md
+mdtail                             # Watch TODO.md (default)
 mdtail README.md                   # Watch specific file
 mdtail *.md                        # Watch all markdown files with tabs
 mdtail TODO.md README.md           # Watch multiple specific files
+mdtail --help                      # Show help
 ```
 
 ### Navigation