[Feature Request] Display session idle time in terminal UI

Question

**Bug Description**
i want to see, from each terminal of claude code session, how much idel time has it been since the latest time i interacted with that session. i think this will be helpful

**Environment Info**
- Platform: darwin
- Terminal: iTerm.app
- Version: 2.1.150
- Feedback ID: 65532fea-1978-4c16-b003-86d35b54ce85

**Errors**
```json
[]
```