Add AI Chatbot as second runnable example

[janrummel]

Summary

• Second runnable example implementing the trigger → ai → data → deliver pattern
• Streaming terminal chat with 5 persona presets (Code Reviewer, Writing Coach, Research Assistant, ELI5, Debate Partner)
• Conversation persistence as JSON with /save, /load, /quit commands
• Interactive API key onboarding on first run (prompt + save to .env)
• 22 new tests (TDD), all green — 72 tests total across the project

Test plan

• uv run pytest -v in examples/ai-chatbot/ — 22 passed
• uv run pytest -v in root — 20 passed
• uv run pytest -v in examples/ai-content-creation/ — 30 passed
• Live test with real API key: streaming response, /save, /quit + auto-save verified
• Site regenerated with new example linked in wizard

🤖 Generated with Claude Code