feat (mcp): Refresh MCP prompts on list changed notification

[MrLesk]

Summary

This PR follows up on https://github.com/google-gemini/gemini-cli/pull/13178 and adds automatic refresh of MCP prompts when the mcp client receives a PromptListChanged Notification.

Details

I used the same logic of refreshing tools and resources but for prompts.

Related Issues

https://github.com/google-gemini/gemini-cli/pull/13178#issuecomment-3620823418

How to Validate

Pre-Merge Checklist

• [ ] Updated relevant documentation and README (if needed)
• [ ] Added/updated tests (if needed)
• [ ] Noted breaking changes (if any)
• [ ] Validated on required platforms/methods:
  • [x] MacOS
    • [x] npm run
    • [ ] npx
    • [ ] Docker
    • [ ] Podman
    • [ ] Seatbelt
  • [ ] Windows
    • [ ] npm run
    • [ ] npx
    • [ ] Docker
  • [ ] Linux
    • [ ] npm run
    • [ ] npx
    • [ ] Docker