fix(交易信号): 修复未追踪仓位时平均单价渲染为 %!f(<nil>) 的问题

- 本地无均价记录时回退使用上游 totalAvgPx
- 跟单模板在无均价时不再输出平均单价行

internal/subscriber/tradesignal/convert.go

@@ -50,8 +50,7 @@ func (c *Converter) Convert(body []byte) (string, map[string]interface{}, error)
 		return "", nil, fmt.Errorf("%w: %v", ErrPositionStore, err)
 	}
 	var opts FormatOptions
-	if snap.HasAvg {
-		avg := snap.AvgPrice
+	if avg, ok := avgPriceFor(snap, out); ok {
 		opts.AvgPrice = &avg
 	}
 	text := Format(out, opts)
@@ -60,12 +59,24 @@ func (c *Converter) Convert(body []byte) (string, map[string]interface{}, error)
 		return "", nil, err
 	}
 	data["formatted"] = text
-	if snap.HasAvg {
-		data["avgPrice"] = snap.AvgPrice
+	if opts.AvgPrice != nil {
+		data["avgPrice"] = *opts.AvgPrice
 	}
 	return "trade." + strings.ToLower(out.Action), data, nil
 }
 
+// avgPriceFor prefers the tracked average and falls back to the upstream
+// totalAvgPx when the tracker never saw the position open.
+func avgPriceFor(snap Snapshot, sig *Signal) (float64, bool) {
+	if snap.HasAvg {
+		return snap.AvgPrice, true
+	}
+	if sig.TotalAvgPx != nil && *sig.TotalAvgPx > 0 {
+		return *sig.TotalAvgPx, true
+	}
+	return 0, false
+}
+
 func (c *Converter) overrideFor(code string) *config.StrategyOverride {
 	if c == nil || len(c.overrides) == 0 || code == "" {
 		return nil