fix: wait for renderer ready before sending tab data

- Wait for did-finish-load event in transfer-tab-data handler
- Await transferTabData before closing file in handlePopOut
- Remove arbitrary 500ms timeout, now uses proper IPC ack flow

electron/main.ts

@@ -497,7 +497,18 @@ ipcMain.handle('transfer-tab-data', async (_event, windowId: number, tabData: an
     if (!win) {
       return { success: false, error: 'Window not found' };
     }
+
+    await new Promise<void>((resolve) => {
+      if (win.webContents.isLoading()) {
+        win.webContents.once('did-finish-load', () => resolve());
+      } else {
+        resolve();
+      }
+      setTimeout(resolve, 2000);
+    });
+
     win.webContents.send('tab-data-received', tabData);
+    log.info('[PopOut] Tab data sent to window:', windowId);
     return { success: true };
   } catch (error: any) {
     log.error('[PopOut] Failed to transfer tab data:', error);