feat(cli): context-aware dev owners with tree branches

- Changed files mode: Analyzes uncommitted changes and suggests reviewers
- Root directory mode: Shows top-level areas with owners
- Subdirectory mode: Shows expertise for current directory
- Tree branch UI (├─, └─) with emojis for visual hierarchy
- Smart defaults: detects context and shows relevant info
- Legacy --all flag for table view
- Always includes helpful tips for next actions

Author: prosdev