fix core dump on export option

hanatui/src/Tui/KeySelectionScreen.cs

@@ -10,9 +10,16 @@ namespace HanaTui.Tui;
 /// </summary>
 public static class KeySelectionScreen
 {
-    // Sentinel values for the non-key choices
-    private const string ManualEntry = "__MANUAL__";
-    private const string ExitChoice  = "__EXIT__";
+    private sealed class KeyChoice
+    {
+        public string Display { get; init; } = "";
+        public string? KeyName { get; init; }  // null = exit, "" = manual entry
+
+        public static readonly KeyChoice Manual = new() { Display = "[ Enter key name manually ]", KeyName = "" };
+        public static readonly KeyChoice Exit   = new() { Display = "[ Exit ]",                    KeyName = null };
+
+        public override string ToString() => Display;
+    }
 
     public static string? Run()
     {
@@ -30,14 +37,11 @@ public static class KeySelectionScreen
             return null;
         }
 
-        // Show client path for reference
         var clientDir = HdbClientLocator.ClientDirectory;
         if (clientDir is not null)
             AnsiConsole.MarkupLine($"[dim]HDB client: {Markup.Escape(clientDir)}[/]\n");
 
-        // Load keys with a spinner
         List<HdbUserstoreKey> keys = [];
-
         AnsiConsole.Status()
             .Spinner(Spinner.Known.Dots)
             .SpinnerStyle(Style.Parse("blue"))
@@ -52,52 +56,34 @@ public static class KeySelectionScreen
             AnsiConsole.MarkupLine("You can still enter a key name manually.\n");
         }
 
-        // Build a plain-string list where the value IS the key name (or sentinel).
-        // We use SelectionPrompt<string> with a display converter so Spectre renders
-        // the label as markup but we always get back the plain key name.
-        var choiceNames = new List<string>();
-        var displayMap  = new Dictionary<string, string>(); // name -> display label
+        // Build typed choices. Display is plain text — never parsed as markup.
+        var choices = keys
+            .Select(k => new KeyChoice { Display = BuildKeyDisplay(k), KeyName = k.Name })
+            .ToList();
+        choices.Add(KeyChoice.Manual);
+        choices.Add(KeyChoice.Exit);
 
-        foreach (var k in keys)
-        {
-            choiceNames.Add(k.Name);
-            displayMap[k.Name] = BuildKeyDisplay(k);
-        }
-
-        choiceNames.Add(ManualEntry);
-        displayMap[ManualEntry] = "[ Enter key name manually ]";
-
-        choiceNames.Add(ExitChoice);
-        displayMap[ExitChoice] = "[ Exit ]";
-
-        var prompt = new SelectionPrompt<string>()
+        var prompt = new SelectionPrompt<KeyChoice>()
             .Title("[bold]Select HDBUSERSTORE key:[/]")
             .PageSize(15)
             .HighlightStyle(Style.Parse("bold dodgerblue1"))
-            .UseConverter(name => displayMap.TryGetValue(name, out var label)
-                ? Markup.Escape(label)
-                : Markup.Escape(name))
-            .AddChoices(choiceNames);
+            .UseConverter(c => Markup.Escape(c.Display))
+            .AddChoices(choices);
 
         var selected = AnsiConsole.Prompt(prompt);
 
-        if (selected == ExitChoice)
-            return null;
+        if (selected.KeyName is null)
+            return null;  // Exit
 
-        if (selected == ManualEntry)
+        if (selected.KeyName == "")
         {
             var manual = AnsiConsole.Ask<string>("[bold]Enter HDBUSERSTORE key name:[/]").Trim();
             return string.IsNullOrWhiteSpace(manual) ? null : manual;
         }
 
-        // selected is already the plain key name
-        return selected;
+        return selected.KeyName;
     }
 
-    /// <summary>
-    /// Builds a plain-text display label (no markup) for a key.
-    /// Spectre's UseConverter renders the returned string as plain text.
-    /// </summary>
     private static string BuildKeyDisplay(HdbUserstoreKey k)
     {
         var sb = new SysText.StringBuilder(k.Name);
@@ -111,12 +97,11 @@ public static class KeySelectionScreen
                 sb.Append(':');
                 sb.Append(k.Port);
             }
-        }
-
-        if (!string.IsNullOrEmpty(k.Tenant))
-        {
-            sb.Append('@');
-            sb.Append(k.Tenant);
+            if (!string.IsNullOrEmpty(k.Tenant))
+            {
+                sb.Append('@');
+                sb.Append(k.Tenant);
+            }
         }
 
         if (!string.IsNullOrEmpty(k.User))