fix(site): 修复 WebKit 渲染下终端顶部控制栏直角溢出 Bug

- 根因分析：Chrome/Safari 等 WebKit 渲染引擎中，子元素的 backdrop-blur-sm 会穿透并破坏父容器 overflow-hidden 的圆角裁切，导致顶部 bg-slate-900 控制栏出现尖锐直角；
- 修复方案：为顶部控制栏显式加上 rounded-t-2xl，为底部内容区显式加上 rounded-b-2xl，彻底解决直角与圆角混杂问题。

apps/site/src/components/agent-install-tabs.astro

@@ -104,8 +104,8 @@ const copy = isEnglish
 
       <!-- Pireel-style Premium Terminal Prompt Window -->
       <div class="mx-auto max-w-3xl rounded-2xl border border-slate-800 bg-slate-950 shadow-2xl overflow-hidden font-mono text-xs sm:text-sm">
-        <!-- Top Window Bar -->
-        <div class="flex items-center justify-between border-b border-slate-800/80 bg-slate-900/90 px-3.5 sm:px-4 py-2.5 backdrop-blur-sm select-none">
+        <!-- Top Window Bar (Explicit rounded-t-2xl to prevent WebKit backdrop-blur overflow) -->
+        <div class="flex items-center justify-between border-b border-slate-800/80 bg-slate-900/90 rounded-t-2xl px-3.5 sm:px-4 py-2.5 backdrop-blur-sm select-none">
           <div class="flex items-center gap-2">
             <div class="flex items-center gap-1.5 mr-1.5">
               <span class="h-2.5 w-2.5 rounded-full bg-[#ff5f57] inline-block opacity-80"></span>
@@ -132,7 +132,7 @@ const copy = isEnglish
         </div>
 
         <!-- Prompt Content Body with Pireel Code Typography & Highlighting -->
-        <div class="p-4 sm:p-6 text-slate-200 leading-relaxed font-mono space-y-3 bg-slate-950/95 select-text">
+        <div class="p-4 sm:p-6 text-slate-200 leading-relaxed font-mono space-y-3 bg-slate-950/95 rounded-b-2xl select-text">
           <p class="text-slate-400 font-semibold text-xs sm:text-sm">
             {isEnglish ? "Please complete EdgeEver deployment online:" : "请在线完成 EdgeEver 部署："}
           </p>