feat: add messageCount parameter to PDF generation logging

Logs total message count (user + AI) sent from plugin for telemetry.
Backward compatible with old plugin versions that don't send this field.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server.js

@@ -132,7 +132,7 @@ app.get('/', (req, res) => {
 app.post('/api/generate_pdf', async (req, res) => {
   const startTime = Date.now();
   const envText = isTest ? '【测试环境】' : '【生产环境】';
-  const { platform, exportCount, language, exportPdf, exportMd, exportTxt, exportDocx, exportJson, exportClipboard, exportNotion, extensionVersion, imageCount, totalImageSizeMB, isPro } = req.body;
+  const { platform, exportCount, language, exportPdf, exportMd, exportTxt, exportDocx, exportJson, exportClipboard, exportNotion, extensionVersion, imageCount, totalImageSizeMB, messageCount, isPro } = req.body;
 
   // PRO status with text emphasis (no ANSI colors for Docker compatibility)
   const userTag = isPro ? '★★★PRO★★★' : '◆FREE◆';
@@ -156,7 +156,7 @@ app.post('/api/generate_pdf', async (req, res) => {
     `---------------[PDF-GEN] ${envText} ${userTag} 收到请求 | 平台: ${platformStr} | 版本: ${versionStr} | 语言: ${langStr}`
   );
   console.log(
-    `  导出: ${exportCount ?? '-'}次 | 格式: ${fmtStr} | 图片: ${imageCount ?? '-'}张 (${totalImageSizeMB ?? '-'}MB)`
+    `  导出: ${exportCount ?? '-'}次 | 格式: ${fmtStr} | 消息: ${messageCount ?? '-'}条 | 图片: ${imageCount ?? '-'}张 (${totalImageSizeMB ?? '-'}MB)`
   );
   console.log(`---------------`);
 
@@ -164,7 +164,7 @@ app.post('/api/generate_pdf', async (req, res) => {
   let browser = null;
 
   try {
-    const { html, showWatermark, imageCount, totalImageSizeMB, codeTheme, textOnlySizeMB } = req.body;
+    const { html, showWatermark, imageCount, totalImageSizeMB, messageCount, codeTheme, textOnlySizeMB } = req.body;
     if (!html) {
       return res.status(400).json({ error: 'Missing html content' });
     }
@@ -199,7 +199,7 @@ app.post('/api/generate_pdf', async (req, res) => {
     // 如果前端未提供（旧版本插件），回退到总大小（向后兼容）
     const effectiveSizeMB = textOnlySizeMB != null ? textOnlySizeMB : htmlSizeMBNum;
 
-    console.log(`[PDF-GEN] [${getElapsed()}] 解析请求完成: HTML ${htmlSizeMB} MB (纯文本=${effectiveSizeMB.toFixed(2)} MB), 图片 ${imgCount} 张 (${imgSizeMB} MB)`);
+    console.log(`[PDF-GEN] [${getElapsed()}] 解析请求完成: HTML ${htmlSizeMB} MB (纯文本=${effectiveSizeMB.toFixed(2)} MB), 消息 ${messageCount || 0} 条, 图片 ${imgCount} 张 (${imgSizeMB} MB)`);
 
     // HTML 大小硬性上限：超过 10 MB 时 Chromium PDF 引擎会崩溃
     // 使用纯文本大小判断（扣除 base64 图片），与前端保持一致