Fix ⌘Q not quitting on macOS

The Quit item was role:"quit" with no accelerator, so ⌘Q was never
bound. Make it a custom action + accelerator "q" dispatched to
Utils.quit(), which emits before-quit so the existing guard (active
transfers / unsaved editors, native confirm dialog) runs instead of the
OS terminating directly. Handled before the manager-open check so ⌘Q
works with the connection manager open too.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/bun/index.ts

@@ -245,6 +245,12 @@ ApplicationMenu.on("application-menu-clicked", (event) => {
 		showAbout();
 		return;
 	}
+	if (action === "quit") {
+		// Utils.quit() emits before-quit -> the guard runs (transfers/unsaved).
+		// Handled before the manager check so ⌘Q quits even with it open.
+		Utils.quit();
+		return;
+	}
 	// the manager is modal to the main window — don't drive main behind it
 	if (manager.isOpen()) return;
 	rpc.send.menuAction({ action });