feat: complete master feature parity with interactive PDF editing, Reveal.js export dialog, Large File Mode, and scoped CSS

src/preload.js

@@ -99,6 +99,7 @@ const ALLOWED_SEND_CHANNELS = [
   'read-file',
   'write-file',
   'write-buffer',
+  'read-buffer',
   'delete-file',
   'ensure-directory',
   'path-exists',
@@ -356,6 +357,8 @@ contextBridge.exposeInMainWorld('electronAPI', {
     rendererReady: () => ipcRenderer.send('renderer-ready'),
     read: (filePath) => ipcRenderer.invoke('read-file', filePath),
     write: (filePath, content) => ipcRenderer.invoke('write-file', { path: filePath, content }),
+    readBuffer: (filePath) => ipcRenderer.invoke('read-buffer', { path: filePath }),
+    writeBuffer: (filePath, buffer) => ipcRenderer.invoke('write-buffer', { path: filePath, buffer }),
     delete: (filePath) => ipcRenderer.invoke('delete-file', filePath),
     ensureDir: (dirPath) => ipcRenderer.invoke('ensure-directory', dirPath),
     exists: (filePath) => ipcRenderer.invoke('path-exists', filePath),