feat: add Document Intelligence Agent Team template (A2A) #5523

[Schlaflied]

Summary

First Hive template implementing the Queen Bee + Worker Bees (A2A) coordination pattern using delegate_to_sub_agent.

Closes #5523

Architecture

Sub-agents (no edge connections, invoked via delegate_to_sub_agent):
  [Researcher]  - Entity/fact extraction
  [Analyst]     - Consistency/contradiction detection
  [Strategist]  - Risk/impact assessment

Key Features

• True A2A coordination: Coordinator declares sub_agents and delegates via delegate_to_sub_agent()
• Isolated execution: Each Worker Bee runs with its own system prompt and conversation context
• Multi-model cross-reference: WorkerModels config allows each specialist to use a different LLM
• Only 2 edges (intake <-> coordinator loop); sub-agents have NO edge connections
• Forever-alive: Continuous document analysis with intake loop

Files Added

• config.py - RuntimeConfig + WorkerModels
• nodes/init.py - 5 NodeSpec definitions
• agent.py - Goal, 2 edges, Agent class
• init.py / main.py - Package exports + CLI
• mcp_servers.json / README.md
• tests/test_structure.py - 21 structural tests

All Tests Pass

• ruff check: All checks passed
• pytest: 21 passed
• python -m document_intelligence_agent_team validate: Graph valid