feat: add Cockpidgey AI agent for PJ

[eric-cunha]

Adds Cockpidgey AI agent to help developers create simple metrics in Cockpit in a guided and interactive way.

Changes

• Added Cockpidgey AI agent specification in .cursor/rules/pj/agents/cockpidgey-ai-agent.mdc

Agent Features

• Guides developers in creating simple metrics (User-level Base Metrics)
• Collects information iteratively and in a friendly manner
• Creates one metric at a time: -users, -volume, or -value
• Ensures Event Logs and necessary records are created
• Follows established patterns in the Experimentation domain