Unity U4: Add MainMenuController.cs - server URL, health check, nav (#49)

Implements MainMenuController for managing server connection and scene navigation.

unity-client/Assets/Scripts/UI/MainMenuController.cs

@@ -0,0 +1,98 @@
+using UnityEngine;
+using UnityEngine.UI;
+using UnityEngine.SceneManagement;
+using TMPro;
+using CommanderAILab.Services;
+
+namespace CommanderAILab.UI
+{
+    /// <summary>
+    /// Main menu scene controller. Handles server URL config,
+    /// connection health check, and navigation to sub-scenes.
+    /// </summary>
+    public class MainMenuController : MonoBehaviour
+    {
+        [Header("Server Config")]
+        [SerializeField] private TMP_InputField serverUrlInput;
+        [SerializeField] private Button connectButton;
+        [SerializeField] private Image statusIndicator;
+        [SerializeField] private TMP_Text statusText;
+
+        [Header("Navigation Buttons")]
+        [SerializeField] private Button collectionButton;
+        [SerializeField] private Button deckBuilderButton;
+        [SerializeField] private Button deckGenButton;
+        [SerializeField] private Button simulatorButton;
+        [SerializeField] private Button scannerButton;
+        [SerializeField] private Button coachButton;
+        [SerializeField] private Button trainingButton;
+
+        [Header("Error Panel")]
+        [SerializeField] private GameObject errorPanel;
+        [SerializeField] private TMP_Text errorText;
+        [SerializeField] private Button retryButton;
+
+        private readonly Color green = new Color(0.2f, 0.8f, 0.2f);
+        private readonly Color red = new Color(0.8f, 0.2f, 0.2f);
+        private readonly Color yellow = new Color(0.8f, 0.8f, 0.2f);
+        private bool isConnected;
+
+        private void Start()
+        {
+            serverUrlInput.text = ApiClient.Instance.BaseUrl;
+            connectButton.onClick.AddListener(OnConnect);
+            retryButton.onClick.AddListener(OnConnect);
+
+            collectionButton.onClick.AddListener(() => LoadScene("Collection"));
+            deckBuilderButton.onClick.AddListener(() => LoadScene("DeckBuilder"));
+            deckGenButton.onClick.AddListener(() => LoadScene("DeckGenerator"));
+            simulatorButton.onClick.AddListener(() => LoadScene("Simulator"));
+            scannerButton.onClick.AddListener(() => LoadScene("Scanner"));
+            coachButton.onClick.AddListener(() => LoadScene("Coach"));
+            trainingButton.onClick.AddListener(() => LoadScene("Training"));
+
+            SetNavEnabled(false);
+            errorPanel.SetActive(false);
+            OnConnect();
+        }
+
+        private void OnConnect()
+        {
+            ApiClient.Instance.BaseUrl = serverUrlInput.text;
+            statusIndicator.color = yellow;
+            statusText.text = "Connecting...";
+            errorPanel.SetActive(false);
+
+            ApiClient.Instance.HealthCheck(alive =>
+            {
+                isConnected = alive;
+                statusIndicator.color = alive ? green : red;
+                statusText.text = alive ? "Connected" : "Disconnected";
+                SetNavEnabled(alive);
+                if (!alive) ShowError("Cannot reach server at " + ApiClient.Instance.BaseUrl);
+            });
+        }
+
+        private void SetNavEnabled(bool enabled)
+        {
+            collectionButton.interactable = enabled;
+            deckBuilderButton.interactable = enabled;
+            deckGenButton.interactable = enabled;
+            simulatorButton.interactable = enabled;
+            scannerButton.interactable = enabled;
+            coachButton.interactable = enabled;
+            trainingButton.interactable = enabled;
+        }
+
+        private void ShowError(string msg)
+        {
+            errorPanel.SetActive(true);
+            errorText.text = msg;
+        }
+
+        private void LoadScene(string sceneName)
+        {
+            if (isConnected) SceneManager.LoadScene(sceneName);
+        }
+    }
+}