[docs] add CLAUDE.md for Claude Code guidance

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+Egg is a MIT-licensed implementation of a Smalltalk-80 derived environment. It's a module-based Smalltalk system that supports multiple runtime platforms (JS, C++, Pharo) and uses image segments for fast module loading.
+
+## Architecture
+
+### Core Components
+
+- **modules/**: Smalltalk source code organized by module (Kernel, Compiler, LMR, etc.)
+- **runtime/**: Platform-specific VM implementations
+  - **runtime/pharo/**: Bootstrap and development platform - main platform for kernel development
+  - **runtime/js/**: JavaScript VM implementation for browser/Node.js
+  - **runtime/cpp/**: Native C++ VM implementation
+- **image-segments/**: Generated binary module files for fast loading (`.json` for JS, `.ems` for native)
+- **docs/**: Sphinx documentation
+
+### Key Concepts
+
+- **Module System**: Each module has its own namespace, no global Smalltalk dictionary
+- **Image Segments**: Binary format for fast module loading without compilation. Generated from Pharo using EggBuilder
+- **Dynamic Binding**: Identifiers resolved at runtime with caching (supports `#doesNotKnow:` like `#doesNotUnderstand:`)
+- **Multi-Platform**: Same Smalltalk code runs on all supported VMs
+- **LMR**: Live Metacircular Runtime - a Smalltalk-in-Smalltalk VM implementation
+
+## Development Commands
+
+### Building Platforms
+
+```bash
+make pharo    # Bootstrap platform (creates egg.image)
+make js       # JavaScript VM
+make cpp      # Native C++ VM (uses Conan + CMake)
+make clean    # Clean all runtimes
+```
+
+### Testing
+
+```bash
+make test     # Run SUnit tests (requires Pharo runtime)
+make test-ci  # Run tests in CI (outputs JUnit XML to test-reports/)
+```
+
+### Pharo Development Environment
+
+```bash
+cd runtime/pharo
+make all           # Create Pharo image
+./pharo-ui egg.image   # Open GUI for development
+```
+
+### Image Segment Generation
+
+```bash
+cd runtime/pharo
+make core-js-segments      # Generate .json segments for JS
+make core-native-segments  # Generate .ems segments for C++/native
+```
+
+### JavaScript Development
+
+```bash
+cd runtime/js
+make all              # Builds interpreter and core segments
+make example-server   # Builds example server with all dependencies
+```
+
+### C++ Development
+
+```bash
+cd runtime/cpp
+make all              # Uses Conan and CMake
+make core-segments    # Generate image segments for native platform
+```
+
+### Webside (Web IDE)
+
+```bash
+cd runtime/pharo
+make webside    # Starts web server on port 9002
+```
+
+## Commit Message Convention
+
+Commit messages must start with a tag indicating the affected area:
+
+```
+<tag>: <short description>
+
+Examples:
+kernel: fix method lookup for proxies
+bootstrap: add support for new primitive
+js: optimize message send
+compiler: handle edge case in parser
+```
+
+## Code Style
+
+See CONTRIBUTING.md for full details. Key rules:
+
+- **Short names**: Single-word temps, usage-primary naming (`done` not `tasksThatHaveBeenDone`)
+- **No comments**: Except public API headers. Refactor instead of commenting
+- **No nested loops**: Factor into separate methods
+- **No keyword-in-keyword**: Use temps instead of `self foo: (self bar: x)`
+- **Autoformatted**: All code is autoformatted
+- **Simplicity over performance**: Let the runtime optimize
+
+## Key Files
+
+- `modules/Kernel/`: Core Smalltalk classes (Object, Class, etc.)
+- `modules/Compiler/`: Smalltalk compiler and parser
+- `modules/LMR/`: Live Metacircular Runtime
+- `runtime/pharo/BaselineOfPowerlang/`: Metacello baseline (groups: `base`, `devel`, `powerlangjs`)
+- `runtime/pharo/Powerlang-Tests/`: Runtime tests