Bind online session browser to canvas, drop IMGUI

- OnlineSessionManager: remove OnGUI/IMGUI state; now a logic-only layer
  exposing Host/Refresh/Join/Disconnect plus Status/IsBusy/IsConnected/
  InSession/Sessions and Changed/SessionsChanged events
- OnlineSessionBrowserUI (new): drives the Servers canvas — 4 buttons,
  session list from Entry Template clones (name + players), row selection,
  state-driven interactability, status footer
- Main scene: attach binder, add status footer line, wire 8 refs; dev
  bootstrap panel disabled
- Online Session Manager.prefab (new)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Assets/Scripts/OnlineSessionBrowserUI.cs

@@ -0,0 +1,168 @@
+using System.Collections.Generic;
+using TMPro;
+using UnityEngine;
+using UnityEngine.UI;
+
+/// <summary>
+/// uGUI binding for <see cref="OnlineSessionManager"/>. Drives the server-browser canvas - Host / Refresh /
+/// pick a row / Join / Disconnect plus a status line - and mirrors the manager's state through its
+/// <see cref="OnlineSessionManager.Changed"/> / <see cref="OnlineSessionManager.SessionsChanged"/> events.
+/// Replaces the old IMGUI browser. Lives on the browser canvas; the session logic stays on the
+/// NetworkManager's <see cref="OnlineSessionManager"/>.
+///
+/// Selection model: Refresh fills the list with clones of <see cref="entryTemplate"/> (each a clickable row
+/// showing name + player count). Clicking a row selects it; Join connects to the selected session. While
+/// connected, only Disconnect is interactable.
+/// </summary>
+public class OnlineSessionBrowserUI : MonoBehaviour
+{
+    [SerializeField] private OnlineSessionManager manager;
+
+    [Header("Buttons")]
+    [SerializeField] private Button hostButton;
+    [SerializeField] private Button refreshButton;
+    [SerializeField] private Button joinButton;
+    [SerializeField] private Button disconnectButton;
+
+    [Header("List")]
+    [Tooltip("Content RectTransform of the session ScrollRect (rows are added here).")]
+    [SerializeField] private RectTransform listContent;
+    [Tooltip("A row prototype kept disabled; cloned once per session. Children named 'Name' and 'Players' carry the text.")]
+    [SerializeField] private GameObject entryTemplate;
+
+    [Header("Status")]
+    [SerializeField] private TMP_Text statusLabel;
+
+    [Tooltip("Background tint of the selected row.")]
+    [SerializeField] private Color selectedTint = new Color(0.26f, 0.52f, 0.96f, 1f);
+    [Tooltip("Background tint of an unselected row.")]
+    [SerializeField] private Color normalTint = new Color(1f, 1f, 1f, 0.05f);
+
+    private struct Row { public string id; public Image image; public GameObject go; }
+    private readonly List<Row> _rows = new List<Row>();
+    private string _selectedId;
+
+    private void Awake()
+    {
+        // The template is the prototype, never shown itself - layout ignores it while disabled.
+        if (entryTemplate) entryTemplate.SetActive(false);
+    }
+
+    private void OnEnable()
+    {
+        if (hostButton) hostButton.onClick.AddListener(OnHost);
+        if (refreshButton) refreshButton.onClick.AddListener(OnRefresh);
+        if (joinButton) joinButton.onClick.AddListener(OnJoin);
+        if (disconnectButton) disconnectButton.onClick.AddListener(OnDisconnect);
+
+        if (manager)
+        {
+            manager.Changed += OnManagerChanged;
+            manager.SessionsChanged += RebuildList;
+        }
+
+        RebuildList();
+        OnManagerChanged();
+    }
+
+    private void OnDisable()
+    {
+        if (hostButton) hostButton.onClick.RemoveListener(OnHost);
+        if (refreshButton) refreshButton.onClick.RemoveListener(OnRefresh);
+        if (joinButton) joinButton.onClick.RemoveListener(OnJoin);
+        if (disconnectButton) disconnectButton.onClick.RemoveListener(OnDisconnect);
+
+        if (manager)
+        {
+            manager.Changed -= OnManagerChanged;
+            manager.SessionsChanged -= RebuildList;
+        }
+    }
+
+    private void OnHost() { if (manager) manager.Host(); }
+    private void OnRefresh() { if (manager) manager.Refresh(); }
+    private void OnJoin() { if (manager && !string.IsNullOrEmpty(_selectedId)) manager.Join(_selectedId); }
+    private void OnDisconnect() { if (manager) manager.Disconnect(); }
+
+    private void OnManagerChanged()
+    {
+        if (!manager) return;
+        if (statusLabel) statusLabel.text = manager.Status;
+        UpdateButtons();
+    }
+
+    private void UpdateButtons()
+    {
+        if (!manager) return;
+        bool busy = manager.IsBusy;
+        bool connected = manager.IsConnected;
+        bool hasSelection = !string.IsNullOrEmpty(_selectedId);
+
+        if (hostButton) hostButton.interactable = !busy && !connected;
+        if (refreshButton) refreshButton.interactable = !busy && !connected;
+        if (joinButton) joinButton.interactable = !busy && !connected && hasSelection;
+        if (disconnectButton) disconnectButton.interactable = !busy && connected;
+    }
+
+    private void RebuildList()
+    {
+        for (int i = 0; i < _rows.Count; i++)
+            if (_rows[i].go) Destroy(_rows[i].go);
+        _rows.Clear();
+
+        if (manager && entryTemplate && listContent)
+        {
+            var sessions = manager.Sessions;
+            bool selectionStillPresent = false;
+
+            for (int i = 0; i < sessions.Count; i++)
+            {
+                var s = sessions[i];
+                var go = Instantiate(entryTemplate, listContent);
+                go.SetActive(true);
+
+                var nameText = FindText(go.transform, "Name");
+                if (nameText) nameText.text = s.Name;
+
+                var playersText = FindText(go.transform, "Players");
+                if (playersText)
+                {
+                    int taken = Mathf.Max(0, s.MaxPlayers - s.AvailableSlots);
+                    playersText.text = $"{taken}/{s.MaxPlayers}";
+                }
+
+                string id = s.Id;                       // capture per-row for the click closure
+                var button = go.GetComponent<Button>();
+                if (button) button.onClick.AddListener(() => Select(id));
+
+                _rows.Add(new Row { id = id, image = go.GetComponent<Image>(), go = go });
+                if (id == _selectedId) selectionStillPresent = true;
+            }
+
+            if (!selectionStillPresent) _selectedId = null;
+        }
+
+        ApplyTints();
+        UpdateButtons();
+    }
+
+    private void Select(string id)
+    {
+        _selectedId = id;
+        ApplyTints();
+        UpdateButtons();
+    }
+
+    private void ApplyTints()
+    {
+        for (int i = 0; i < _rows.Count; i++)
+            if (_rows[i].image)
+                _rows[i].image.color = _rows[i].id == _selectedId ? selectedTint : normalTint;
+    }
+
+    private static TMP_Text FindText(Transform root, string childName)
+    {
+        var t = root.Find(childName);
+        return t ? t.GetComponent<TMP_Text>() : null;
+    }
+}