Fixes#8
- Added visitorCount to WorldState and implemented increment/decrement functions.
- Updated WebSocket connection/disconnection handlers in events.ts to manage visitor count, broadcast events, and trigger Timmy greetings/farewells.
- Implemented generateVisitorGreeting and generateVisitorFarewell in agent.ts to create personalized messages.
- Modified websocket.js to listen for visitor_count events and pass them to ui.js.
- Updated ui.js and index.html to display the live visitor count with responsive design.
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