fix: 改用下载到文件再执行，修复中文乱码

根因: irm/iwr 文本解码时将 UTF-8 中文替换为 ?，
字符串在进入 iex 之前就已损坏。
改用 iwr -OutFile 写入原始字节到临时文件再执行，
绕过文本解码链路，彻底修复编码问题。

quick-start.html

@@ -296,7 +296,7 @@
                 <button class="copy-btn" onclick="copyCode('windows-code')">📋 复制</button>
                 <div class="code-block" id="windows-code">
 <span class="code-line">$key='YOUR_API_KEY'</span>
-<span class="code-line">iex (irm https://gitea.sususu.cf/sususu/xcodecli-shells/raw/branch/main/setup-claude-code.ps1)</span>
+<span class="code-line">$f="$env:TEMP\xc.ps1";iwr -useb https://gitea.sususu.cf/sususu/xcodecli-shells/raw/branch/main/setup-claude-code.ps1 -OutFile $f;& $f</span>
                 </div>
             </div>
         </div>
@@ -345,7 +345,7 @@
             const windowsCode = document.getElementById('windows-code');
             windowsCode.innerHTML = `
 <span class="code-line">$key='${apiKey}'</span>
-<span class="code-line">iex (irm https://gitea.sususu.cf/sususu/xcodecli-shells/raw/branch/main/setup-claude-code.ps1)</span>
+<span class="code-line">$f="$env:TEMP\xc.ps1";iwr -useb https://gitea.sususu.cf/sususu/xcodecli-shells/raw/branch/main/setup-claude-code.ps1 -OutFile $f;& $f</span>
             `.trim();
 
             // 更新 Unix 代码