fix: prevent messages from disappearing and show streaming status immediately
Fixed two critical streaming bugs:
1. Messages disappearing after streaming:
- Keep streaming content visible until reload completes
- Added 300ms delay before reloading to let server finalize
- Clear streaming state AFTER messages are loaded, not before
- Don't clear messages if reload returns empty (race condition)
2. Streaming status not showing immediately:
- Remove 300ms fade-in animation for statusFadeAnim
- Set opacity to 1 immediately when streaming starts
- This makes '(co is thinking)' visible right away
Changes:
- statusFadeAnim.setValue(1) instead of animating from 0
- Reordered stream completion: wait → reload → clear state
- Added safety check in loadMessages to preserve messages on empty reload
- Reduced delay from 500ms to 300ms for better responsiveness
The streaming content now remains visible during the transition from
streaming to finalized messages, preventing the UI from going blank.