Show active sessions in status command with stats
The status command now displays information about active sessions:
- Lists all active sessions (channel topics and DMs)
- Shows number of turns in each session
- Shows how long each session has been active
- Shows last update time for each session
Example output:
- Active sessions (2):
- **channel foo > topic bar**: 5 turns, last updated 30s ago (active for 1.5h)
- **DM with user@example.com**: 3 turns, last updated 2m ago (active for 45m)
Co-Authored-By: Claude (claude-opus-4-5) <noreply@anthropic.com>