docs: Add Claude AI guidance and PHP requirement (#24)

- Introduce CLAUDE.md to provide project context and development
instructions for AI assistants.
- Update README.md to explicitly state the PHP 8.2+ requirement.
- Add .claude to .gitignore to prevent committing AI-generated files.

Author: SmetDenis

.gitignore

@@ -17,3 +17,4 @@ vendor
 phpunit.xml
 *.cache
 tests/fixtures/lib-*
+.claude

CLAUDE.md

@@ -0,0 +1,59 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+This is **jbzoo/composer-graph**, a PHP CLI tool that renders dependency graphs from composer.json and composer.lock files. It generates HTML visualizations using Mermaid.js to display package dependencies, PHP extensions, dev dependencies, and suggested packages.
+
+## Development Commands
+
+### Primary Commands
+- `make update` - Install/update all dependencies using Composer
+- `make build` - Install dependencies and build PHAR file
+- `make test-all` - Run full test suite and code style checks
+- `make test` - Run PHPUnit tests only
+- `make codestyle` - Run code style checks and fixes
+
+### Testing
+- `vendor/bin/phpunit` - Run PHPUnit tests directly
+- Tests are in `tests/` directory with fixtures in `tests/fixtures/`
+- PHPUnit configuration in `phpunit.xml.dist`
+
+### Code Quality Tools
+The project uses `jbzoo/toolbox-dev` which provides various code quality tools:
+- `vendor/bin/php-cs-fixer` - PHP CS Fixer for code formatting
+- `vendor/bin/phan` - Static analysis
+- Various other tools available in `vendor/bin/`
+
+## Architecture
+
+### Core Classes
+- **`ComposerGraph`** (`src/ComposerGraph.php`) - Main class that builds dependency graphs using Mermaid.js
+- **`Collection`** (`src/Collection.php`) - Manages packages and their relationships
+- **`Package`** (`src/Package.php`) - Represents individual packages with dependencies
+- **`Helper`** (`src/Helper.php`) - Utility functions for package processing
+- **`Commands/Build`** (`src/Commands/Build.php`) - CLI command implementation using JBZoo CLI framework
+
+### Key Dependencies
+- **JBZoo Libraries**: Uses `jbzoo/cli`, `jbzoo/mermaid-php`, `jbzoo/data`, `jbzoo/utils`
+- **Symfony Console**: For CLI interface (`symfony/console`)
+- **Mermaid.js**: Graph visualization via `jbzoo/mermaid-php` wrapper
+
+### Main Flow
+1. Parse `composer.json` and `composer.lock` files from specified root directory
+2. Build package collection with dependencies, dev dependencies, extensions
+3. Generate Mermaid.js graph syntax with nodes and links
+4. Output as HTML file with embedded Mermaid visualization or raw Mermaid format
+
+### Binary Entry Points
+- `composer-graph` - Shell script wrapper
+- `composer-graph.php` - Main PHP entry point
+- PHAR file is built for distribution
+
+## File Structure
+- `src/` - Main source code (PSR-4: JBZoo\ComposerGraph namespace)
+- `tests/` - PHPUnit tests with fixture projects
+- `resources/` - Example images and assets
+- `build/` - Build artifacts and reports
+- `Makefile` - Development commands (includes jbzoo/codestyle tasks)

Dockerfile

@@ -10,7 +10,7 @@
 # @see        https://github.com/JBZoo/Composer-Graph
 #
 
-FROM php:8.1-cli-alpine
+FROM php:8.4-cli-alpine
 RUN mv "$PHP_INI_DIR/php.ini-production" "$PHP_INI_DIR/php.ini"
 
 ADD https://github.com/mlocati/docker-php-extension-installer/releases/latest/download/install-php-extensions /usr/local/bin/

README.md

@@ -29,6 +29,8 @@
 
 ## Installation
 
+**Requirements:** PHP 8.2+
+
 ```shell
 composer require        jbzoo/composer-graph # For a specific project
 composer global require jbzoo/composer-graph # As global tool