Add response timing display for interactive sessions

## Feature Request: Response Timing Display

### Problem
Currently, there's no way to see how long each individual response takes within an interactive Claude session. This would be valuable for:

• Performance monitoring
• Understanding response complexity
• Debugging slow queries

### Proposed Solution
Add a setting or flag (e.g., --show-timing or claude.showResponseTime: true) that displays response time after each answer in interactive mode.

### Example Output
Human: What is 2+2?

4

⏱️ Response time: 1.23 seconds