v1.8.1: 修复下载得到 txt —— Blob 必须带 MIME（否则 Chrome 嗅探内容把 HTML 错误页存成 .txt）；新增内容魔数校验，拦截 200+HTML 错误页与空内容

manifest.json

@@ -1,7 +1,7 @@
 {
   "manifest_version": 3,
   "name": "B站评论助手",
-  "version": "1.8.0",
+  "version": "1.8.1",
   "description": "B站网页版关键词评论助手：按搜索关键词找视频，默认模拟真人（打开视频页、滚到评论区、逐字输入、点发布），也可快速API直发；支持下载当前页视频；带防重复记录、可中断执行与页面实时进度浮层。",
   "permissions": ["storage", "tabs", "scripting", "sidePanel", "downloads", "declarativeNetRequest"],
   "host_permissions": [