docs: add tool simulator example

[ybdarrenwang]

Description

Adds comprehensive documentation and examples for the ToolSimulator framework introduced in strands-agents/evals. Demonstrates realistic multi-turn agent evaluation scenarios with simulated tools.

Key additions:

• Complete smart home example (tool_simulator.py) showcasing all three simulation modes working together with shared state
• Multi-agent workflow demonstration with agent-as-tool pattern using hvac_control_assistant sub-agent
• State inspection utilities showing how to track state changes across tool invocations

Related Issues

strands-agents/evals#93

Type of Change

• New content

Checklist

• I have read the CONTRIBUTING document
• My changes follow the project's documentation style
• I have tested the documentation locally using mkdocs serve
• Links in the documentation are valid and working

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