scaffold-bot-handler

Scaffold a new bot conversation handler in packages/bot following the BaseChatBot + CompletionHandler strategy pattern. Generates ChatBot subclass, streaming variant, CompletionHandler, Controller with fluent builder, and registers in app/main.py. Use when user says "create a bot handler", "scaffold bot handler", "new chat bot", "add bot type", "generate bot integration", "build a chatbot for X", or "add bot…