Add WebSocket support for real-time messaging with @hono/node-ws

[Copilot]

This PR implements real-time messaging functionality using WebSocket connections to transform the MLack application into a functional chat interface.

Changes Made

🔧 Dependencies

• Added @hono/node-ws for WebSocket support
• Added @types/ws for TypeScript definitions

🌐 New Endpoints

• Root Page (/): Interactive chat interface with "Hello, world!" message and real-time messaging
• WebSocket (/ws): WebSocket endpoint for real-time message broadcasting

💬 Chat Interface Features

• Clean, responsive UI with connection status indicator
• Real-time message display with styled message bubbles
• Text input with both button click and Enter key support
• Automatic message broadcasting to all connected clients
• Connection status feedback (Connected/Disconnected/Connecting)

🧪 Testing & Quality

• Added comprehensive tests for new endpoints
• All existing tests continue to pass
• ESLint compliance maintained
• TypeScript compilation without errors

📚 Documentation

• Updated README.md with new features and API documentation
• Added WebSocket usage examples

Implementation Details

The WebSocket implementation uses @hono/node-ws to create a /ws endpoint that:

1. Maintains a Set of connected clients
2. Broadcasts incoming messages to all connected clients
3. Handles connection/disconnection lifecycle
4. Converts message formats for compatibility

The root page serves a complete HTML interface with:

• Modern CSS styling with a card-based layout
• JavaScript WebSocket client that auto-connects
• Real-time message rendering with auto-scroll
• Input validation and error handling

Screenshot

The interface shows the "Hello, world!" message at the top, connection status, message history, and input controls as specified in the requirements.

Testing

All functionality has been tested:

• ✅ WebSocket connections establish successfully
• ✅ Messages broadcast to all connected clients
• ✅ UI responds correctly to user interactions
• ✅ Connection status updates appropriately
• ✅ Both click and Enter key sending work
• ✅ All existing functionality remains intact

Fixes #3.

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