Auto-size NavigationView pane to fit the widest sidebar label

The previously hardcoded OpenPaneLength="185" clipped English labels
like "Software information", "Donate to the author", and "Backup and
restore", as well as longer translations such as de-DE
"Programmeinstellungen" / "Backup-Wiederherstellung", pt-BR
"Configurações do Programa", tr-TR "Yedekleme ve Geri Yükleme", and
ru-RU "Поблагодарить автора".

Computes the required pane length at startup from the actual labels:
the natural width of each item's text (via FormattedText at the
NavigationView's typeface/size/DPI) plus role-specific chrome
measured against iNKORE.UI.WPF.Modern v0.10.2's NavigationViewItem
template — 100px for expandable parents (icon + chevron slot), 74px
for icon-only footer leaves, 67px for nested leaves. Result is
clamped to [185, 400] so section items with short text don't shrink
the pane below the original width and no single pathological label
eats the content area. Since language changes trigger
SingleInstance.Restart(), the calculation runs exactly once per
launch.

Author: KamilDev

ContextMenuManager/MainWindow.xaml

@@ -32,7 +32,6 @@
             AlwaysShowHeader="False"
             IsBackButtonVisible="Collapsed"
             IsSettingsVisible="False"
-            OpenPaneLength="185"
             SelectionChanged="NavView_SelectionChanged">
 
             <!--  Main content area  -->

ContextMenuManager/MainWindow.xaml.cs

@@ -11,6 +11,7 @@
 using System.Linq;
 using System.Windows;
 using System.Windows.Input;
+using System.Windows.Media;
 using DrawingSize = System.Drawing.Size;
 
 namespace ContextMenuManager
@@ -63,6 +64,7 @@ public MainWindow()
 
             // Populate navigation items from AppString
             BuildNavigation();
+            AdjustPaneWidthToContent();
 
             // First-run language download prompt
             Loaded += (_, _) => FirstRunDownloadLanguage();
@@ -149,6 +151,50 @@ private void BuildNavigation()
             }
         }
 
+        // Sizes OpenPaneLength to fit the widest item label so translations don't get clipped.
+        // Chrome values are measured against iNKORE.UI.WPF.Modern v0.10.2's NavigationViewItem template
+        // (Segoe UI 14pt): an item's rendered width = LPad + content + RPad, where LPad/RPad depend
+        // on whether the item has an icon or an expand chevron.
+        private void AdjustPaneWidthToContent()
+        {
+            const double chevronChrome = 100;  // expandable parent (icon + chevron slot)
+            const double iconChrome = 74;      // leaf with icon (footer items)
+            const double plainChrome = 67;     // nested leaf, no icon
+            const double minPaneLength = 185;
+            const double maxPaneLength = 400;
+
+            var typeface = new Typeface(NavView.FontFamily, NavView.FontStyle, NavView.FontWeight, NavView.FontStretch);
+            var pixelsPerDip = VisualTreeHelper.GetDpi(this).PixelsPerDip;
+            var fontSize = NavView.FontSize > 0 ? NavView.FontSize : 14;
+
+            double maxRequired = 0;
+            foreach (var item in EnumerateNavigationItems())
+            {
+                if (item.Content is not string text || text.Length == 0) continue;
+
+                double chrome = item.MenuItems.Count > 0 ? chevronChrome
+                              : item.Icon != null ? iconChrome
+                              : plainChrome;
+
+                var ft = new FormattedText(
+                    text,
+                    CultureInfo.CurrentUICulture,
+                    FlowDirection.LeftToRight,
+                    typeface,
+                    fontSize,
+                    Brushes.Black,
+                    pixelsPerDip);
+
+                double required = ft.Width + chrome;
+                if (required > maxRequired) maxRequired = required;
+            }
+
+            NavView.OpenPaneLength = Math.Clamp(
+                Math.Ceiling(maxRequired),
+                minPaneLength,
+                maxPaneLength);
+        }
+
         private static NavigationViewItem MakeSectionItem(string content, string glyph)
         {
             var item = new NavigationViewItem() { Content = content, Icon = new FontIcon { Glyph = glyph } };