Describe the bug

When Minimize to tray is enabled, Kudu cannot be quit through any normal means. On macOS this goes further: the app blocks system shutdown/restart — macOS waits for Kudu to quit, and the shutdown hangs until the user force-quits Kudu.

To reproduce

1. Enable Minimize to tray in Settings (macOS, Kudu 1.44.1, also reproducible from current main).
2. Press Cmd+Q (or Kudu menu → Quit Kudu, or right-click the Dock icon → Quit). The window disappears, but the app keeps running (menu bar icon still there, processes alive).
3. Shut down or restart the Mac → shutdown hangs on Kudu until it is force-quit.

Root cause

In src/main/index.ts, the main window's close handler calls e.preventDefault() unconditionally whenever minimizeToTray is enabled:

mainWindow.on('close', (e) => {
  const currentSettings = getSettings()
  if (currentSettings.minimizeToTray && mainWindow && !mainWindow.isDestroyed()) {
    e.preventDefault()
    mainWindow.hide()
  }
})

In Electron, app.quit() (which is what Cmd+Q, the menu Quit, and the OS shutdown Apple Event go through) first tries to close all windows — and a preventDefault() in any window's close handler aborts the entire quit. The before-quit handler never sets any "we are quitting" flag, so there is no path for quit to get past the interceptor.

The tray menu's Quit item works around this with mainWindow.removeAllListeners('close'), which is why quitting from the tray is currently the only way out.

Expected behavior

Closing the window with Minimize to tray enabled should hide it to the tray (as today), but an explicit quit (Cmd+Q / menu / Dock / OS shutdown) should actually quit the app.

Also affected: update restarts

The same interceptor breaks the auto-updater on macOS: autoUpdater.quitAndInstall() closes all windows before app emits before-quit, so with minimize to tray enabled the prevented close silently blocks the "restart to install update" flow too (autoRestart/daemon updates never complete).

Suggested fix

The standard Electron pattern: set an isQuitting flag on before-quit (and before-quit-for-update for the updater path) and let close proceed when it's set. Fix proposed in #240.

Environment

• Kudu 1.44.1 (also present in current main)
• macOS 15 (Darwin 25.5.0), Apple Silicon