autoresearch iter 7: share body field extraction across push channels

email, telegram and lark each re-implemented the title/content/level lookup
with only their markup differing, and each carried a dead content := ""
initialization that every branch overwrote. Three small helpers in template.go
now own that logic.

backend/plugins/domain/message_gateway/push/email.go

@@ -37,22 +37,8 @@ func (p *EmailPusher) Send(ctx context.Context, cfg Config, target string, body
 		return "", errors.New("email: target email address is required")
 	}
 
-	title := defaultTitle
-	if t, ok := body["title"].(string); ok && t != "" {
-		title = t
-	}
-
-	content := ""
-	if c, ok := body["content"].(string); ok && c != "" {
-		content = c
-	} else {
-		// 自动格式化 map
-		var parts []string
-		for k, v := range body {
-			parts = append(parts, fmt.Sprintf("<p><b>%s</b>: %v</p>", k, v))
-		}
-		content = strings.Join(parts, "")
-	}
+	title := bodyTitle(body)
+	content := bodyContent(body, "<p><b>%s</b>: %v</p>", "")
 
 	// 邮件头和体
 	from := cfg.Key

backend/plugins/domain/message_gateway/push/lark.go

@@ -154,27 +154,9 @@ func (p *LarkPusher) Send(ctx context.Context, cfg Config, _ string, body map[st
 		}
 	} else {
 		// 2. 如果无模板，默认生成一个精美的飞书互动卡片
-		title := defaultTitle
-		if t, ok := body["title"].(string); ok && t != "" {
-			title = t
-		}
-
-		content := ""
-		if c, ok := body["content"].(string); ok && c != "" {
-			content = c
-		} else {
-			// 兜底：如果连 content 都没有，把 body 里的所有值拼成 markdown
-			var parts []string
-			for k, v := range body {
-				parts = append(parts, fmt.Sprintf("**%s**: %v", k, v))
-			}
-			content = strings.Join(parts, "\n")
-		}
-
-		level := levelInfo
-		if l, ok := body["level"].(string); ok && l != "" {
-			level = strings.ToUpper(l)
-		}
+		title := bodyTitle(body)
+		content := bodyContent(body, "**%s**: %v", "\n")
+		level := bodyLevel(body)
 
 		// 根据级别确定飞书卡片头部的背景色模板
 		headerColor := "blue"

backend/plugins/domain/message_gateway/push/telegram.go

@@ -55,24 +55,9 @@ func (p *TelegramPusher) Send(ctx context.Context, cfg Config, target string, bo
 	}
 	baseURL = strings.TrimSuffix(baseURL, "/")
 
-	title := defaultTitle
-	if t, ok := body["title"].(string); ok && t != "" {
-		title = t
-	}
-	content := ""
-	if c, ok := body["content"].(string); ok && c != "" {
-		content = c
-	} else {
-		var parts []string
-		for k, v := range body {
-			parts = append(parts, fmt.Sprintf("<b>%s</b>: %v", k, v))
-		}
-		content = strings.Join(parts, "\n")
-	}
-	level := levelInfo
-	if l, ok := body["level"].(string); ok && l != "" {
-		level = strings.ToUpper(l)
-	}
+	title := bodyTitle(body)
+	content := bodyContent(body, "<b>%s</b>: %v", "\n")
+	level := bodyLevel(body)
 
 	var text string
 	if template != "" {

backend/plugins/domain/message_gateway/push/template.go

@@ -76,3 +76,32 @@ func formatValue(v any) string {
 		return fmt.Sprintf("%v", v)
 	}
 }
+
+// bodyTitle returns the notification title, falling back to the default.
+func bodyTitle(body map[string]any) string {
+	if t, ok := body["title"].(string); ok && t != "" {
+		return t
+	}
+	return defaultTitle
+}
+
+// bodyContent returns the notification body, rendering every entry with format
+// (a "%s … %v" pair) and joining them with sep when no content field is given.
+func bodyContent(body map[string]any, format, sep string) string {
+	if c, ok := body["content"].(string); ok && c != "" {
+		return c
+	}
+	parts := make([]string, 0, len(body))
+	for k, v := range body {
+		parts = append(parts, fmt.Sprintf(format, k, v))
+	}
+	return strings.Join(parts, sep)
+}
+
+// bodyLevel returns the upper-cased notification level, falling back to INFO.
+func bodyLevel(body map[string]any) string {
+	if l, ok := body["level"].(string); ok && l != "" {
+		return strings.ToUpper(l)
+	}
+	return levelInfo
+}