feat: please evaluate and add anonymous metrics collection with enduser controls

### Which area does this relate to?

- [x] CLI code
- [ ] SPEC or COMPLIANCE file
- [ ] Other doc files

### What kind of feature are you proposing?

Developer experience / ergonomics

### What would you like to see?

A2A CLI Usage Analytics.

### Why is this important?

A2A CLI is new. Understanding anonymous usage & adoption metrics is essential for the growth of CLI.

At the same time, it is essential to respect user privacy. `scarf.sh` seem to provides a clear path for data collection and user controls to opt out.

### Who benefits from this feature?

The A2A CLI Development team + community can prioritize bug fixes & feature improvements according to usage metrics.

### Would you be interested in helping build this feature?

No — just proposing the idea

### Additional context

_No response_

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct