Fix #1271: constrain web tab header titles

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: JoshuaRowePhantom

Phantom.Workspaces.Tests/TabHeaderViewModelTests.cs

@@ -351,6 +351,31 @@ public void TabHeaderViewModel_WebTabHeaderTemplate_UsesCharacterEllipsisTrimmin
         Assert.Equal(TextTrimming.CharacterEllipsis, titleTextBlock.TextTrimming);
     }
 
+    [AvaloniaFact(Timeout = 15_000)]
+    public void WebTabHeaderTemplate_LongTitle_TextBlockIsTrimmedToConfiguredMaxWidth()
+    {
+        var viewModel = new WebTabHeaderViewModel
+        {
+            Title = "Bug: \"Microsoft.Extensions.AI.UsageContent\" leaks as literal text in assistant replies on tool-only turns",
+        };
+
+        var titleTextBlock = InflateTabHeaderTitleTextBlock(viewModel, ResolveWebTabHeaderTemplate());
+
+        Assert.Equal(TextTrimming.CharacterEllipsis, titleTextBlock.TextTrimming);
+        Assert.Equal(240, titleTextBlock.MaxWidth);
+    }
+
+    [AvaloniaFact(Timeout = 15_000)]
+    public void WebTabHeaderTemplate_LongTitle_ToolTipStillExposesFullTitle()
+    {
+        const string longTitle = "Bug: Web tab titles are not length-limited and full page titles overflow the tab strip";
+        var viewModel = new WebTabHeaderViewModel { Title = longTitle };
+
+        var titleTextBlock = InflateTabHeaderTitleTextBlock(viewModel, ResolveWebTabHeaderTemplate());
+
+        Assert.Equal(longTitle, ToolTip.GetTip(titleTextBlock));
+    }
+
     [AvaloniaFact(Timeout = 15_000)]
     public void TabHeaderViewModel_DefaultTemplate_DoesNotTrim()
     {

Phantom.Workspaces/Templates/TabHeaderItemTemplates.axaml

@@ -52,7 +52,8 @@
             <StackPanel Orientation="Horizontal" Spacing="4">
                 <TextBlock Text="{Binding Title}"
                            ToolTip.Tip="{Binding Title}"
-                           TextTrimming="CharacterEllipsis" />
+                           TextTrimming="CharacterEllipsis"
+                           MaxWidth="240" />
                 <ItemsControl ItemsSource="{Binding Items}">
                     <ItemsControl.ItemsPanel>
                         <ItemsPanelTemplate>