feat(research): Integrate TransferGraph visualization with improved flow clarity

## Complete TransferGraph Module Integration

### New Features:
- **TransferGraph module** (346 lines): Clean separation of data + rendering
- **Configurable rendering** via RenderConfig (icons, titles, summaries)
- **DFS path-finding** built into graph structure
- **Professional formatting** with thousand separators (100,000.00)
- **Improved visual flow** with vertical guides and spacing

### Visual Improvements:
- Vertical pipe guides (│) showing continuous flow
- Downward arrows (↓) making transfer direction obvious
- "TO:" labels explicitly showing destination wallets
- Extra spacing between sibling branches
- Clear branch indicators (├ for mid-branches, └ for last)

### Test Infrastructure:
- 9 comprehensive TransferGraph tests (all passing)
- Helper functions for creating valid test states
- Fixed all 6 broken unit tests
- Mock data demos for instant visualization testing

### Code Stats:
- +1,942 lines in research_agent.rs
- 130+ lines removed (old manual rendering)
- Net improvement: cleaner, more maintainable, better UX

### Example Output:
```
🏦 EXCHANGE Binance Deposit
      └──────→ [100,000.00 SVMAI]
                ↓
             TO: SuspectWallet

      🎯 SUSPECT Investigation Target
            │
            ├──────→ [30,000.00 SVMAI]
            │         ↓
            │      TO: MixerEntry
```

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: 0xrinegade