Port example agents from gaia6 as reference implementations

[kovtcharov]

Summary

Port the 7 example agents from gaia6/examples/ as reference implementations for the Agent Hub and community contributions.

Examples to Port

File	Description
file_watcher_agent.py	Agent that watches file system changes
hardware_advisor_agent.py	Agent that advises on hardware configuration
mcp_config_based_agent.py	Agent configured via MCP config file
mcp_time_server_agent.py	MCP time server integration example
mcp_windows_system_health_agent.py	Windows system health monitoring via MCP
notes_agent.py	Note-taking and recall agent
sd_agent_example.py	Stable Diffusion image generation example

Acceptance Criteria

• All 7 examples ported to gaia7 examples/ directory
• Each example runs standalone with python examples/<name>.py
• README with descriptions and usage instructions
• Examples serve as templates for Agent Hub community contributions