feat(terminal): open .md file links in built-in markdown viewer

Clicking a .md file link in the terminal opens it in a resizable
markdown viewer dialog with syntax highlighting. Cmd+click opens
the file externally instead. Non-.md files always open externally.

Author: maskar

electron/ipc/channels.ts

@@ -100,6 +100,7 @@ export enum IPC {
 
   // File links
   OpenPath = 'open_path',
+  ReadFileText = 'read_file_text',
 
   // Notifications
   ShowNotification = 'show_notification',

electron/ipc/register.ts

@@ -458,6 +458,11 @@ export function registerAllHandlers(win: BrowserWindow): void {
     return shell.openPath(args.filePath);
   });
 
+  ipcMain.handle(IPC.ReadFileText, (_e, args) => {
+    validatePath(args.filePath, 'filePath');
+    return fs.readFileSync(args.filePath, 'utf8');
+  });
+
   // --- System ---
   ipcMain.handle(IPC.GetSystemFonts, () => getSystemMonospaceFonts());
 

electron/preload.cjs

@@ -92,6 +92,7 @@ const ALLOWED_CHANNELS = new Set([
   'get_system_fonts',
   // File links
   'open_path',
+  'read_file_text',
   // Notifications
   'show_notification',
   'notification_clicked',