docs: add Goose integration tutorial

[pmady]

Summary

Add a tutorial or example showing gpu-mcp-server integrated with Goose for an end-to-end GPU-aware agentic workflow.

What to cover

• Goose configuration for gpu-mcp-server (already in README)
• Example prompts that use GPU metrics:
  • "Which GPU has the most free memory?"
  • "Is any GPU thermally throttling?"
  • "Show me which processes are using GPU 0"
• Screenshot or terminal recording of the interaction

Acceptance criteria

• Tutorial in docs/tutorials/goose-integration.md
• Example Goose session showing tool calls and responses
• Linked from README

Difficulty: Beginner — documentation and testing with Goose