Part 2: hands-on console chat app (#499)

[jongalloway]

Summary

Adds the new Part 2: Build a Chat App — a hands-on, code-first console app that attendees build from scratch before ever seeing a template. Resolves #499.

This is the first part of the workshop rewrite.

What's included

• Part 2 - Build Chat App/ChatApp/ — a net10.0 console project
  • Secrets-first configuration (user-secrets; no hardcoded keys)
  • IChatClient created from AzureOpenAIClient via .AsIChatClient()
  • Chat loop with conversation history
  • Streaming responses (GetStreamingResponseAsync)
  • A middleware pipeline (.AsBuilder().UseLogging(...))
• Part 2 - Build Chat App/README.md — step-by-step walkthrough

Teaching flow

Attendees write the code themselves to learn the fundamentals, then meet the
template later (Part 4). RAG is added by hand in Part 3.

Models & provider

• Provider: Azure AI Foundry (Azure OpenAI)
• Chat model: gpt-4.1-mini

Validation

• ✅ Builds clean against net10.0 (dotnet build -c Release, 0 warnings, 0 errors)
• ⏳ Runtime validation against a live Azure AI Foundry resource is deferred to the E2E test pass (End-to-end test pass vs a real Azure AI Foundry resource #504)

Notes

• bin/ and obj/ are gitignored — only source is committed.
• Adapted with attribution from Steve Sanderson's dotnet-ai-workshop.