fix(ios): resolve rootViewController from connected UIWindowScene (fixes launch crash under UIScene lifecycle)

[vingulati]

Problem

On the modern Flutter iOS template (Flutter ≥ 3.35, which uses the UIScene lifecycle — a SceneDelegate extending FlutterSceneDelegate + a UIApplicationSceneManifest), UIApplication.shared.delegate.window is always nil because the window is owned by the scene, not the app delegate.

SwiftTwilioVoicePlugin.init() does:

let appDelegate = UIApplication.shared.delegate
guard let controller = appDelegate?.window??.rootViewController as? FlutterViewController else {
    fatalError("rootViewController is not type FlutterViewController")
}

Because appDelegate.window is nil, this fatalErrors during plugin registration — crashing the entire host app at launch, before any Dart runs. Stack trace bottoms out at SwiftTwilioVoicePlugin.init() → register(with:) → GeneratedPluginRegistrant → didInitializeImplicitFlutterEngine.

Fix

Resolve the window from UIApplication.shared.connectedScenes when the app delegate has no window, and — since the method/event channels are also wired in register(with:) — degrade gracefully (return) instead of fatalError if the root view controller isn't attached yet during registration.

No behavior change for classic (non-scene) apps: appDelegate.window is used first when present.

Testing

Reproduced the launch crash on a Flutter 3.44.7 app using the UIScene template (iOS 26 simulator). With this change the host app launches normally and the plugin's channels work. Verified against tag 0.3.2+2.

🤖 Generated with Claude Code

[cybex-dev]

Hi @vingulati,

thank you for your contribution though this has already been fixed by PR #320 merged yesterday.