Desktop: trim a long session tab label instead of letting it push the + off the strip

tests/DodoSSH.Client.App.Layout.Tests/SessionTabRowTests.cs

@@ -250,6 +250,42 @@ public sealed class SessionTabRowTests : IAsyncLifetime
             Token);
     }
 
+    /// <remarks>
+    /// A label is whatever the host was called or the address typed into the palette, and nothing bounded it:
+    /// one long one pushed the "+" past the edge of the strip, behind a scroll bar nobody looks for.
+    /// </remarks>
+    [Fact]
+    public async Task ALongLabelIsTrimmed_AndLeavesThePlusOnTheStrip()
+    {
+        await LayoutHarness.OnTheUiThreadAsync(
+            () =>
+            {
+                var label = string.Concat(Enumerable.Repeat("a-very-long-host-name-", 12));
+
+                shell.Tabs.Add(new TerminalTabViewModel(1, label, "deploy@long.internal:22"));
+
+                var strip = new SessionTabRow { DataContext = shell, TabCommand = shell.SelectTabCommand };
+                var window = LayoutHarness.HostAtMinimumSize(
+                    strip, LayoutHarness.MinimumWidth, LayoutHarness.MinimumHeight);
+
+                try
+                {
+                    var text = strip.GetVisualDescendants().OfType<TextBlock>()
+                        .Single(block => string.Equals(block.Text, label, StringComparison.Ordinal));
+
+                    text.Bounds.Width.ShouldBeLessThanOrEqualTo(200);
+                    ToolTip.GetTip(text).ShouldBe(label, "the whole of it is still one hover away");
+
+                    LayoutHarness.Unreachable(window).ShouldBeEmpty();
+                }
+                finally
+                {
+                    window.Close();
+                }
+            },
+            Token);
+    }
+
     /// <remarks>
     /// v5b's tab, unlike the pill it replaced, paints no fill at all until it is either active or hovered —
     /// so "the plus differs from a tab" can no longer be proven against a resting, inactive one, which reads