🎨 Phase 2: Video Player with AI Tutor Integration

## Phase 2: Enhanced UI

Integrate the AI Tutor chat alongside the video player.

### Tasks
- [ ] Build side-by-side layout (Video | Chat Tutor)
- [ ] Implement chat interface within player view
- [ ] Add "Ask about this timestamp" quick action
- [ ] Display cited timestamps as clickable video links
- [ ] Add loading states for AI responses
- [ ] Implement chat history persistence

### Acceptance Criteria
- Split-screen design: video on left, chat on right
- Users can ask questions while watching
- Clicking timestamp citations jumps to video position
- Chat history saved per course/video
- Responsive layout (collapse chat on mobile)

### Tech Stack
- React split-pane components
- Streaming API responses
- Video player API integration
- Markdown rendering for AI responses