feat: enhance IRC support with display name handling, private channel tracking, and connection identification

src/EchoHub.Client/UI/Chat/ChatMessageManager.cs

@@ -381,6 +381,9 @@ public sealed class ChatMessageManager
     private List<ChatLine> FormatMessage(MessageDto message)
     {
         var time = FormatTime(message.SentAt);
+        // Show the display name, but keep color + click identity keyed to the username
+        // so they stay consistent with the user list and profile lookups.
+        var senderName = message.SenderDisplayName ?? message.SenderUsername;
         var senderColor = HexColorHelper.ParseHexColor(message.SenderNicknameColor)
             ?? NickColorHelper.GetAttribute(message.SenderUsername);
 
@@ -394,7 +397,7 @@ public sealed class ChatMessageManager
             var displayContent = EmojiHelper.ReplaceEmoji(message.Content);
             var contentLines = displayContent.Split('\n');
 
-            var header = HeaderSegments(time, message.SenderUsername, senderColor);
+            var header = HeaderSegments(time, senderName, senderColor);
             header.AddRange(ChatColors.SplitMentions(contentLines[0].TrimEnd('\r')));
             lines.Add(new ChatLine(header));
 
@@ -413,7 +416,7 @@ public sealed class ChatMessageManager
                 1 => $"[{attachments[0].Kind.ToString().ToLowerInvariant()}]",
                 _ => $"[{attachments.Count} attachments]",
             };
-            var header = HeaderSegments(time, message.SenderUsername, senderColor);
+            var header = HeaderSegments(time, senderName, senderColor);
             header.Add(new(summary, null));
             lines.Add(new ChatLine(header));
         }

src/EchoHub.Client/UI/ListSources/ChannelListSource.cs

@@ -18,6 +18,7 @@ public class ChannelListSource : IListDataSource
     private readonly Dictionary<string, int> _unreadCounts = [];
     private readonly HashSet<string> _protectedChannels = [];
     private readonly HashSet<string> _mentionChannels = [];
+    private readonly HashSet<string> _privateChannels = [];
     private string _activeChannel = string.Empty;
 
     public event NotifyCollectionChangedEventHandler? CollectionChanged;
@@ -32,7 +33,8 @@ public class ChannelListSource : IListDataSource
     private static readonly Attribute MentionAttr = new(new Color(230, 140, 60), Color.None);
 
     public void Update(List<string> channels, Dictionary<string, int> unread, string activeChannel,
-        IReadOnlySet<string>? protectedChannels = null, IReadOnlySet<string>? mentionChannels = null)
+        IReadOnlySet<string>? protectedChannels = null, IReadOnlySet<string>? mentionChannels = null,
+        IReadOnlySet<string>? privateChannels = null)
     {
         _channelNames.Clear();
         _channelNames.AddRange(channels);
@@ -45,6 +47,9 @@ public class ChannelListSource : IListDataSource
         _mentionChannels.Clear();
         if (mentionChannels is not null)
             _mentionChannels.UnionWith(mentionChannels);
+        _privateChannels.Clear();
+        if (privateChannels is not null)
+            _privateChannels.UnionWith(privateChannels);
         _activeChannel = activeChannel;
         MaxItemLength = channels.Count > 0 ? channels.Max(c => c.Length + 6) : 0;
         if (!SuspendCollectionChangedEvent)
@@ -67,8 +72,12 @@ public class ChannelListSource : IListDataSource
         var normalAttr = listView.GetAttributeForRole(VisualRole.Normal);
         var focusAttr = listView.GetAttributeForRole(VisualRole.Focus);
         var prefix = isActive ? "> " : "  ";
-        // Trailing * marks password-protected (+k) channels
-        var channelText = _protectedChannels.Contains(name) ? $"#{name}*" : $"#{name}";
+        // Trailing * marks password-protected (+k) channels; ~ marks private (unlisted) ones
+        var channelText = $"#{name}";
+        if (_protectedChannels.Contains(name))
+            channelText += "*";
+        if (_privateChannels.Contains(name))
+            channelText += "~";
         var badge = hasUnread ? $" ({unread})" : "";
 
         // Resolve Transparent backgrounds to the view's actual background

src/EchoHub.Client/UI/MainWindow.cs

@@ -1317,8 +1317,11 @@ public sealed partial class MainWindow : Runnable
     /// </summary>
     private void RefreshChannelList()
     {
+        var privateChannels = _channelNames
+            .Where(n => _channelPublic.TryGetValue(n, out var isPublic) && !isPublic)
+            .ToHashSet();
         _channelListSource.Update(_channelNames, _messageManager.GetUnreadCounts(), _messageManager.CurrentChannel,
-            _channelProtected, _messageManager.MentionChannels);
+            _channelProtected, _messageManager.MentionChannels, privateChannels);
         _channelList.Source = _channelListSource;
 
         // Restore selection to current channel
@@ -1394,6 +1397,10 @@ public sealed partial class MainWindow : Runnable
             var text = roleTag.Length > 0
                 ? $"{statusIcon} {roleTag} {name}"
                 : $"{statusIcon} {name}";
+            // Users connected only via the IRC gateway get a tag — they lack client features
+            // (encryption, attachments, profiles), which is useful context in conversation.
+            if (u.IsIrc)
+                text += " [irc]";
             // Fall back to the deterministic per-nick palette so user-list colors
             // match the same user's messages in chat.
             var nameColor = HexColorHelper.ParseHexColor(u.NicknameColor)