Add CLAUDE.md and AGENTS.md, update .gitignore

.gitignore

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 # Yarn cache
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+*.chat
+.jupyter_ystore.db

AGENTS.md

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+CLAUDE.md

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
+
+This is `jupyter_ai_router`, a core message routing layer for Jupyter AI. It's a JupyterLab extension that provides foundational message routing functionality, automatically detecting new chat sessions and routing messages to registered callbacks based on message type (slash commands vs regular messages).
+
+## Architecture
+
+### Core Components
+
+- **MessageRouter** (`jupyter_ai_router/router.py`): Central routing class that manages chat connections and message callbacks
+- **RouterExtension** (`jupyter_ai_router/extension.py`): Jupyter server extension that initializes the router and listens for chat events
+- **Frontend Plugin** (`src/index.ts`): JupyterLab frontend extension for client-side integration
+- **API Handler** (`jupyter_ai_router/handlers.py`): Simple health check endpoint
+
+### Key Dependencies
+
+- `jupyterlab-chat>=0.17.0`: Core chat functionality and YChat document handling
+- `jupyter-collaboration>=4.0.0`: Real-time collaboration features and event system
+- `pycrdt`: CRDT (Conflict-free Replicated Data Type) for message handling
+
+### Message Flow
+
+1. RouterExtension listens for `jupyter_collaboration` chat room initialization events
+2. When new chat detected, retrieves YChat document and connects to MessageRouter
+3. MessageRouter observes YChat message streams and routes to registered callbacks
+4. Messages are classified as slash commands (starting with `/`) or regular messages
+5. Appropriate callbacks are invoked with `(room_id, message)` parameters
+
+## Development Commands
+
+### Initial Setup
+
+```bash
+# Install development dependencies
+jlpm
+
+# Install Python package in development mode
+pip install -e ".[test]"
+
+# Link extension to JupyterLab
+jupyter labextension develop . --overwrite
+
+# Enable server extension
+jupyter server extension enable jupyter_ai_router
+```
+
+### Building
+
+```bash
+# Build TypeScript and JupyterLab extension (development)
+jlpm build
+
+# Production build
+jlpm build:prod
+
+# Watch mode (rebuilds on changes)
+jlpm watch
+```
+
+### Testing
+
+```bash
+# Run Python tests with coverage
+pytest -vv -r ap --cov jupyter_ai_router
+
+# Run JavaScript/TypeScript tests
+jlpm test
+
+# Run integration tests (Playwright)
+cd ui-tests && jlpm test
+```
+
+### Code Quality
+
+```bash
+# Run all linting and formatting
+jlpm lint
+
+# Check code style without fixing
+jlpm lint:check
+
+# Individual tools
+jlpm eslint          # Fix TypeScript/JavaScript issues
+jlpm prettier       # Fix formatting
+jlpm stylelint       # Fix CSS issues
+```
+
+### Development Workflow
+
+```bash
+# Clean build artifacts
+jlpm clean:all
+
+# Full development setup from scratch
+jlpm dev:install
+
+# Uninstall development setup
+jlpm dev:uninstall
+```
+
+## Code Style
+
+### TypeScript/JavaScript
+
+- Single quotes for strings
+- No trailing commas
+- Arrow functions preferred
+- Interface names must start with `I` and be PascalCase
+- 2-space indentation
+
+### Python
+
+- Follow standard Python conventions
+- Use type hints where appropriate
+- Inherit from `LoggingConfigurable` for components that need logging
+
+## Extension Integration
+
+Other Jupyter extensions can access the router via settings:
+
+```python
+router = self.serverapp.web_app.settings.get("jupyter-ai", {}).get("router")
+
+# Register callbacks
+def on_new_chat(room_id: str, ychat: YChat):
+    print(f"New chat: {room_id}")
+
+def on_slash_command(room_id: str, message: Message):
+    print(f"Slash command: {message.body}")
+
+router.observe_chat_init(on_new_chat)
+router.observe_slash_cmd_msg(room_id, on_slash_command)
+router.observe_chat_msg(room_id, on_regular_message)
+```
+
+## Version Compatibility
+
+- Python 3.9-3.13
+- JupyterLab 4.x
+- Handles both jupyter-collaboration v3+ and v2.x compatibility through version detection
+
+## Testing Strategy
+
+- **Unit tests**: Jest for TypeScript, pytest for Python
+- **Integration tests**: Playwright via Galata for full JupyterLab integration
+- **Coverage**: Aim for comprehensive test coverage, especially for routing logic