fix(windows): polish hotkeys, user list, titlebar, and PM window

- Suppress the system ding on global hotkeys/PTT and the user-list Enter
  key by setting SuppressKeyPress (Handled alone leaves WM_CHAR to beep).
- Preserve the user-list keyboard selection across talking/mute refreshes
  instead of resetting it on every Items.Clear().
- Include the connected server name in the main window titlebar.
- Close the private-message window on Escape.
- Show the PM window without an owner so focus is no longer trapped to it
  and the main window can be worked in while a PM is open.

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

clients/windows/VoiceCat.App/Forms/MainForm.cs

@@ -42,14 +42,16 @@ public partial class MainForm : Form
     private ToolStripMenuItem _miJoinVoice = null!;
     private ToolStripMenuItem _miScreenShare = null!;
 
-    public MainForm(VoiceCatClient client, uint selfUserId, string nickname)
+    public MainForm(VoiceCatClient client, uint selfUserId, string nickname, string serverName)
     {
         InitializeComponent();
         _client = client;
         _selfUserId = selfUserId;
         _nickname = nickname;
 
-        Text = $"VoiceCat — {nickname}";
+        Text = string.IsNullOrWhiteSpace(serverName)
+            ? $"VoiceCat — {nickname}"
+            : $"VoiceCat — {nickname} @ {serverName}";
 
         _client.EventReceived += OnEvent;
         _client.LevelChanged += OnLevelChanged;
@@ -69,7 +71,7 @@ public partial class MainForm : Form
         tvChannels.DoubleClick += TvChannels_DoubleClick;
         tvChannels.KeyDown += TvChannels_KeyDown;
         lstUsers.DoubleClick += (_, _) => OpenUserTuning();
-        lstUsers.KeyDown += (_, e) => { if (e.KeyCode == Keys.Enter) OpenUserTuning(); };
+        lstUsers.KeyDown += (_, e) => { if (e.KeyCode == Keys.Enter) { OpenUserTuning(); e.Handled = e.SuppressKeyPress = true; } };
 
         // Compose
         txtCompose.KeyDown += TxtCompose_KeyDown;
@@ -599,6 +601,11 @@ public partial class MainForm : Form
 
     private void RefreshUserList()
     {
+        // Preserve the keyboard selection across the rebuild: clearing the list resets
+        // SelectedIndex to -1, which would throw focus around every time a talking/mute
+        // indicator toggles. Capture the selected user id and reselect it afterwards.
+        uint? prevSel = (lstUsers.SelectedItem as UserListItem)?.UserId;
+
         lstUsers.BeginUpdate();
         lstUsers.Items.Clear();
         foreach (var user in _users.Values
@@ -612,6 +619,15 @@ public partial class MainForm : Form
             if (user.SelfDeafened || user.ServerDeafened) label += " (deafened)";
             lstUsers.Items.Add(new UserListItem(user.Id, label));
         }
+        if (prevSel is uint sel)
+        {
+            for (int i = 0; i < lstUsers.Items.Count; i++)
+                if (lstUsers.Items[i] is UserListItem item && item.UserId == sel)
+                {
+                    lstUsers.SelectedIndex = i;
+                    break;
+                }
+        }
         lstUsers.EndUpdate();
         UpdateStatusLabel();
     }
@@ -854,7 +870,7 @@ public partial class MainForm : Form
             _pttEngaged = true;
             _feedback.PlaySound(SoundEvent.Ptt);
         }
-        e.Handled = true;
+        e.Handled = e.SuppressKeyPress = true;
     }
 
     private void MainForm_HotkeyDown(object? sender, KeyEventArgs e)
@@ -865,23 +881,24 @@ public partial class MainForm : Form
         {
             case Keys.V:
                 BtnMicToggle_Click(null, EventArgs.Empty);
-                e.Handled = true;
                 break;
             case Keys.S:
                 BtnScreenShareToggle_Click(null, EventArgs.Empty);
-                e.Handled = true;
                 break;
             case Keys.M:
                 chkMute.Checked = !chkMute.Checked;
                 ApplySelfMute();
-                e.Handled = true;
                 break;
             case Keys.D:
                 chkDeafen.Checked = !chkDeafen.Checked;
                 ApplySelfMute();
-                e.Handled = true;
                 break;
+            default:
+                return;
         }
+        // A handled hotkey: suppress the follow-on WM_CHAR so the focused control
+        // (channel tree / user list) doesn't emit the system "ding".
+        e.Handled = e.SuppressKeyPress = true;
     }
 
     private void MainForm_KeyUp(object? sender, KeyEventArgs e)
@@ -890,7 +907,7 @@ public partial class MainForm : Form
         if (e.KeyCode != _pttKey || _micStreamId == 0) return;
         _client.SetPushToTalk(false);
         _pttEngaged = false;
-        e.Handled = true;
+        e.Handled = e.SuppressKeyPress = true;
     }
 
     // ── Channel navigation ────────────────────────────────────────────────────
@@ -940,13 +957,17 @@ public partial class MainForm : Form
             win = new PrivateMessageForm(_client, userId, nick, _selfUserId);
             win.FormClosed += (_, _) => _pmWindows.Remove(userId);
             _pmWindows[userId] = win;
-            win.Show(this);
+            // Show without an owner: an owned form is forced to stay above MainForm and pulls
+            // focus back to itself, so the main window can't be worked in while a PM is open.
+            // OnFormClosed already closes any open PM windows, so this doesn't leak.
+            win.Show();
         }
         else
         {
             if (win.WindowState == FormWindowState.Minimized)
                 win.WindowState = FormWindowState.Normal;
-            win.BringToFront();
+            // Raise it for this explicit user-initiated open without the owner-style focus trap.
+            win.Activate();
         }
         return win;
     }