Refactor chat UI and token generation logic, and handle token generation errors

Author: vraspar

mobile/examples/phi-3/ios/LocalLLM/LocalLLM/ContentView.swift

@@ -1,3 +1,6 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
 import SwiftUI
 
 

mobile/examples/phi-3/ios/LocalLLM/LocalLLM/GenAIGenerator.mm

@@ -18,8 +18,10 @@ @interface GenAIGenerator () {
 
 @implementation GenAIGenerator
 
-typedef std::chrono::high_resolution_clock Clock;
+typedef std::chrono::steady_clock Clock;
 typedef std::chrono::time_point<Clock> TimePoint;
+static std::unique_ptr<OgaModel> model = nullptr;
+static std::unique_ptr<OgaTokenizer> tokenizer = nullptr;
 
 typedef std::chrono::steady_clock Clock;
 typedef std::chrono::time_point<Clock> TimePoint;