fix(trader): restore TP/SL after partial_close to prevent unprotected positions

## Problem
- User reported: After partial_close, remaining position has NO TP/SL protection
- Root cause: Binance automatically cancels TP/SL orders when position size changes
- Impact: Remaining position exposed to unlimited risk (爆仓风险)

## Why TP/SL disappears
```
Opening:
  Position: 0.130 BTC
  TP order: 0.130 BTC ✓
  SL order: 0.130 BTC ✓

After 50% partial_close:
  Position: 0.065 BTC (remaining)
  TP order: 0.130 BTC ❌ Quantity mismatch → Binance cancels
  SL order: 0.130 BTC ❌ Quantity mismatch → Binance cancels
  → Remaining position has NO protection
```

## Solution

### Code changes (trader/auto_trader.go:1278-1305)

After partial_close execution, restore TP/SL with new quantity:

```go
// If AI provides new TP/SL prices
if decision.NewStopLoss > 0 || decision.NewTakeProfit > 0 {
    // Re-set SL with remaining quantity
    at.trader.SetStopLoss(symbol, side, remainingQuantity, newStopLoss)
    // Re-set TP with remaining quantity
    at.trader.SetTakeProfit(symbol, side, remainingQuantity, newTakeProfit)
} else {
    // WARNING: Remaining position has NO protection
    log.Printf("⚠️⚠️⚠️ 警告: 剩余仓位无止盈止损保护")
}
```

### Prompt updates

**Updated files**:
- prompts/adaptive.txt (line 171)
- prompts/default.txt (line 190)
- prompts/nof1.txt (line 334)

**Key change**: Emphasize AI MUST provide `new_stop_loss` and `new_take_profit` in `partial_close` decisions:

```markdown
- **partial_close**: Fill `close_percentage` (1-100),
  **STRONGLY RECOMMEND** providing `new_stop_loss` AND `new_take_profit`
  to protect remaining position (otherwise NO stop protection)
```

## Benefits

- ✅ Risk control: Remaining position protected after partial_close
- ✅ Clear warning: Logs explicit warning if AI doesn't provide new TP/SL
- ✅ AI guidance: Updated prompts emphasize importance of new TP/SL
- ✅ Backwards compatible: Works even if AI doesn't provide (just warns)

## Testing checklist

- [ ] Partial_close with new_stop_loss & new_take_profit → TP/SL restored
- [ ] Check Binance UI shows TP/SL orders after partial_close
- [ ] Partial_close without new TP/SL → Warning logged
- [ ] Remaining quantity matches TP/SL order quantity

Related: partial-close-tpsl-bug.md

prompts/default.txt

@@ -187,7 +187,7 @@ THINK: trend=down, 等待确认
 - **开仓** (`open_long/open_short`)：必须填写 `position_size_usd`、`leverage`、`stop_loss`、`take_profit`、`risk_usd`；`reasoning` 写出信号与风险回报。
 - **平仓** (`close_long/close_short`)：`reasoning` 说明平仓原因（达到目标、触发失效条件等）。
 - **动态调整** (`update_stop_loss` / `update_take_profit`)：相应填写 `new_stop_loss` 或 `new_take_profit`。
-- **部分平仓** (`partial_close`)：需填写 `close_percentage`（1-100），说明目的（如锁定利润）。
+- **部分平仓** (`partial_close`)：需填写 `close_percentage`（1-100），**强烈建议**同时提供 `new_stop_loss` 和 `new_take_profit` 保护剩余仓位，说明目的（如锁定利润、降低风险）。
 - **观望或持有** (`wait/hold`)：`reasoning` 必须说明观望或继续持有的原因（例如信号不足、冷却中、趋势未变）。
 
 ### 仓位大小计算