fix(ui): guard sidebar row at min drag and widen system-icon match

DrawRow asserted on a zero-width InvisibleButton when the window was
dragged below the pop-out hit threshold — the row now drops out cleanly
under 2px of remaining sidebar width, and the pop-out button only
splits off when there's room for both hit areas. The trailing pop-out
icon is hidden too when its strip is collapsed, so the row stays as a
single selectable strip on extreme drags.

System icon path: ResolveTabIcon used to look only at the first key in
SelectedChannels, so a System tab whose first filter happened to be a
generic ChatType slipped through to Comment. The resolve now walks
every key and keeps the first non-Comment match, and a final
case-insensitive name match flips the icon to fa-cog when the user's
filter set falls completely outside the channel-type table.

HellionChat/Ui/Components/Sidebar.cs

@@ -110,10 +110,22 @@ internal sealed class Sidebar
 
         var origin = ImGui.GetCursorScreenPos();
         var avail = ImGui.GetContentRegionAvail().X;
-        var tabHitWidth = MathF.Max(0f, avail - PopOutHitWidth);
 
-        // Tab hit area sits left of the pop-out button so the two never
+        // Drop the row entirely when the sidebar is dragged below the width
-        // steal each other's clicks.
+        // of a single hit target. ImGui's InvisibleButton asserts on a
+        // zero-width size, which crashes the whole window at min-drag.
+        if (avail < 2f)
+        {
+            ImGui.PopID();
+            return;
+        }
+
+        // Only split off a separate pop-out hit area when there's room for
+        // both buttons. Below that, the whole row stays as a single
+        // selectable strip without the pop-out affordance.
+        var hasPopOut = avail > PopOutHitWidth + 4f;
+        var tabHitWidth = hasPopOut ? avail - PopOutHitWidth : avail;
+
         ImGui.InvisibleButton("row", new Vector2(tabHitWidth, RowHeight));
         var rowHovered = ImGui.IsItemHovered();
         if (ImGui.IsItemClicked())
@@ -144,13 +156,17 @@ internal sealed class Sidebar
             ImGui.EndPopup();
         }
 
+        var popHovered = false;
+        if (hasPopOut)
+        {
             ImGui.SameLine(0f, 0f);
             ImGui.InvisibleButton("popout", new Vector2(PopOutHitWidth, RowHeight));
-        var popHovered = ImGui.IsItemHovered();
+            popHovered = ImGui.IsItemHovered();
             if (ImGui.IsItemClicked())
                 LogPopOutStub(tab);
+        }
 
-        if (rowHovered || popHovered)
+        if (hasPopOut && (rowHovered || popHovered))
         {
             using (_fonts.FontAwesome.Push())
             {
@@ -174,12 +190,23 @@ internal sealed class Sidebar
         if (tab.IsTempTab)
             return FontAwesomeIcon.Envelope;
 
-        // Channel-type fallback. The v1.5.6 TabIconGlyphResolver did the
+        // Channel-type fallback. Walk every selected key, not just the first,
-        // same thing — picks the first selected channel and maps its
+        // so a System tab that filters multiple system-flavoured ChatTypes
-        // ChatType to a category icon so tabs without a user-set icon
+        // still picks up fa-cog when one of the later keys carries the match.
-        // still look distinct.
+        // The Comment default only wins when every key falls into the
-        if (tab.SelectedChannels.Count > 0)
+        // generic-text bucket (Say / Yell / Shout etc.).
-            return ResolveByChannelType(tab.SelectedChannels.Keys.First());
+        foreach (var chatType in tab.SelectedChannels.Keys)
+        {
+            var glyph = ResolveByChannelType(chatType);
+            if (glyph != FontAwesomeIcon.Comment)
+                return glyph;
+        }
+
+        // Last-resort name match for tabs that filter exotic ChatTypes the
+        // mapping above doesn't cover — keeps the System tab visually
+        // distinct even with a custom channel set.
+        if (tab.Name.Contains("system", StringComparison.OrdinalIgnoreCase))
+            return FontAwesomeIcon.Cog;
 
         return FontAwesomeIcon.Comment;
     }