fix: 清理调试日志，确认下载机制

根因：Chrome '下载前询问保存位置' 设置与 saveAs 冲突。
关闭该设置后下载正常。background 通过 storage.session 传 base64 并下载。

web-to-ppt/background.js

@@ -173,15 +173,11 @@ chrome.runtime.onMessage.addListener((message, sender, sendResponse) => {
 
   // 下载 PPTX（从 storage 读取 base64）
   if (message?.type === "WEB_TO_PPT_DOWNLOAD") {
-    console.log("[WebToPPT] download handler triggered");
     (async () => {
       const stored = await chrome.storage.session.get(['pptxBase64', 'pptxFilename']);
-      console.log('[WebToPPT] stored keys:', Object.keys(stored), 'dataLen:', stored.pptxBase64?.length);
       if (!stored.pptxBase64) throw new Error('没有待下载的数据');
       const dataUrl = 'data:application/vnd.openxmlformats-officedocument.presentationml.presentation;base64,' + stored.pptxBase64;
-      console.log('[WebToPPT] calling downloads.download, url length:', dataUrl.length);
       await chrome.downloads.download({ url: dataUrl, filename: stored.pptxFilename });
-      console.log('[WebToPPT] download completed');
       await chrome.storage.session.remove(['pptxBase64', 'pptxFilename']);
       return { ok: true };
     })()