📝 **Task:** Implement `route_turn(turn: dict) -> str` that returns one of `'haiku'`, `'sonnet'`, `'opus'` based on these rules (in priority order): 1. If `turn['escalate']` is truthy → `'opus'` 2. Else if `turn['tool_count']` ≥ 1 → `'sonnet'` 3. Else if `len(turn['text'])` < 80 chars AND no images → `'haiku'` 4. Else → `'sonnet'` (default) Then implement `estimate_cost(model: str, input_tokens: int, output_tokens: int) -> float`. Use these per-1M-token prices: Haiku 1/5, Sonnet 3/15, Opus 5/25 (input/output USD). Finally, exercise the router with 4 sample turns + print results. Expected output (4 lines): ``` haiku sonnet opus 0.051 ``` 📋 Implement the function above. Tests run automatically. 💡 **Hint:** Re-read the theory if stuck.