Add Cursor cloud agent skill

[dgroomes]

Summary

• add a new llm-agent skill for installing the Cursor CLI and managing Cursor Cloud Agents
• document the observed cloud secret behavior for the configured caak secret
• include tested REST API examples for listing, inspecting, creating, following up, stopping, and deleting agents

Testing

• installed the Cursor CLI with curl https://cursor.com/install -fsS | bash
• verified agent --version
• verified caak is exposed in this environment without printing its value
• verified GET /v0/me, GET /v0/repositories, GET /v0/models, GET /v0/agents, GET /v0/agents/{id}, GET /v0/agents/{id}/conversation
• smoke tested POST /v0/agents, POST /v0/agents/{id}/followup, POST /v0/agents/{id}/stop, and DELETE /v0/agents/{id}