清理：移除未使用的 openFiles IPC、优化 setModified 避免每次按键重建标签 DOM

main.js

@@ -84,9 +84,9 @@ function stopWatching() {
   }
 }
 
-async function showOpenDialog(multi) {
+async function showOpenDialog() {
   const result = await dialog.showOpenDialog(mainWindow, {
-    properties: multi ? ['openFile', 'multiSelections'] : ['openFile'],
+    properties: ['openFile'],
     filters: [
       { name: 'Markdown 文件', extensions: ['md', 'markdown', 'txt'] },
       { name: '所有文件', extensions: ['*'] }
@@ -131,7 +131,7 @@ function switchActiveFile(filePath) {
 // Open single file via dialog
 ipcMain.handle('dialog:openFile', async () => {
   try {
-    const files = await showOpenDialog(false);
+    const files = await showOpenDialog();
     if (files && files.length > 0) {
       const content = readFileContent(files[0]);
       activeFilePath = files[0];
@@ -145,27 +145,6 @@ ipcMain.handle('dialog:openFile', async () => {
   }
 });
 
-// Open multiple files via dialog
-ipcMain.handle('dialog:openFiles', async () => {
-  try {
-    const files = await showOpenDialog(true);
-    if (files && files.length > 0) {
-      const results = [];
-      for (const fp of files) {
-        try {
-          const content = readFileContent(fp);
-          results.push({ filePath: fp, content });
-        } catch (err) {
-          results.push({ filePath: fp, error: err.message });
-        }
-      }
-      return results;
-    }
-    return null;
-  } catch (err) {
-    return { error: err.message };
-  }
-});
 
 ipcMain.handle('file:read', async (event, filePath) => {
   try {