feat(demos): add AG2 multi-agent research team with Plano orchestration

[faridun-ag2]

Summary

• Adds a new demo demos/agent_orchestration/multi_agent_ag2/ showcasing AG2 multi-agent orchestration via Plano
• AG2 runs an internal GroupChat (researcher + analyst) behind a single Plano endpoint — Plano sees one agent, while multi-agent collaboration happens inside
• Key differentiator vs the existing CrewAI/LangChain demo: there, each framework = one agent = one endpoint; here, AG2 runs a team of agents behind one endpoint

What's included

• ag2/research_agent.py — FastAPI server with OpenAI-compatible /v1/chat/completions (streaming + non-streaming) and /health; AG2 GroupChat with researcher + analyst agents
• config.yaml — Plano config registering the agent on port 10530 with plano_orchestrator_v1 router
• run_demo.sh / start_agents.sh — one-command startup scripts
• pyproject.toml — dependencies (ag2[openai], fastapi, uvicorn, openai)
• openai_protocol.py — shared streaming utility (copied from existing demo)
• README.md — full documentation with architecture diagram and quickstart

Test plan

• GET /health returns {"status":"healthy","agent":"ag2_research_team"}
• POST /v1/chat/completions streaming works end-to-end through Plano
• POST /v1/chat/completions non-streaming works end-to-end through Plano
• AG2 GroupChat runs exactly 2 LLM calls (researcher → analyst) with no extra round-trips
• pre-commit hooks pass (black, yaml, secrets scan)

[faridun-ag2]

Hey @adilhafeez, I've added an AG2 multi-agent demo to the repo!

This shows a unique pattern - AG2's GroupChat (researcher + analyst) running behind a single Plano endpoint. Unlike the existing CrewAI/LangChain demo where each framework = one agent, here AG2 runs an internal team that Plano sees as one agent.

Would love your feedback when you get a chance!