refactor(HTMLBuf): delegate fallback to HTML() method

Reduce code duplication by calling c.HTML() for fallback cases:
- When template rendering fails
- When HTMLRender is not configured
- When HTMLRender is not a *template.Template

This ensures consistent behavior between HTMLBuf and HTML methods.

context.go

@@ -514,27 +514,28 @@ func (c *Context) HTML(code int, name string, obj any) {
 }
 
 // HTMLBuf 先将 HTML 模板渲染到 buffer, 成功后再写入状态码和响应体.
+// 如果模板渲染失败或不支持缓冲渲染，则回退到标准的 HTML 方法.
 func (c *Context) HTMLBuf(code int, name string, obj any) {
 	if c.engine != nil && c.engine.HTMLRender != nil {
 		if tpl, ok := c.engine.HTMLRender.(*template.Template); ok {
 			var buf bytes.Buffer
 			err := tpl.ExecuteTemplate(&buf, name, obj)
-			if err != nil {
+			if err == nil {
-				errMsg := fmt.Errorf("failed to render HTML template '%s': %w", name, err)
+				// 渲染成功，写入响应
-				c.AddError(errMsg)
-				c.ErrorUseHandle(http.StatusInternalServerError, errMsg)
-				return
-			}
 				c.Writer.Header().Set("Content-Type", "text/html; charset=utf-8")
 				c.Writer.WriteHeader(code)
 				c.Writer.Write(buf.Bytes())
 				return
 			}
+			// 渲染失败，记录错误后回退到 HTML()
+			errMsg := fmt.Errorf("failed to render HTML template '%s': %w", name, err)
+			c.AddError(errMsg)
+			c.ErrorUseHandle(http.StatusInternalServerError, errMsg)
+			// 继续执行回退逻辑
 		}
-	// 默认简单输出
+	}
-	c.Writer.Header().Set("Content-Type", "text/html; charset=utf-8")
+	// 回退到标准 HTML 方法（处理无模板引擎或其他渲染器的情况）
-	c.Writer.WriteHeader(code)
+	c.HTML(code, name, obj)
-	c.Writer.Write(fmt.Appendf(nil, "<!-- HTML rendered for %s -->\n<pre>%v</pre>", name, obj))
 }
 
 // Redirect 执行 HTTP 重定向