feat: display reasoning content while streaming under '(co is thinking)'

Previously, when reasoning was streaming, only '(co is thinking)' appeared
without showing the actual reasoning content being generated.

Changes:
- Show LiveStatusIndicator with 'thinking' status when reasoning streams
- Display reasoning content below in a styled container while streaming
- Use similar styling to expanded reasoning blocks:
- Semi-transparent background
- Left border accent
- Consistent typography and spacing

Now the UI shows:
1. '(co is thinking)' - status indicator
2. The actual reasoning text as it streams in real-time
3. Proper visual styling matching finalized reasoning blocks

This improves transparency by letting users see the agent's thought
process in real-time instead of hiding it until completion.