Give the application a settings area built from what really exists

src/DodoSSH.Client.Shell/ViewModels/KnownHostsViewModel.cs

@@ -106,10 +106,19 @@ internal sealed class KnownHostRowViewModel(
 internal sealed partial class KnownHostsViewModel : ObservableObject
 {
     private readonly VaultViewModel vault;
+    private readonly Action? onBack;
 
-    internal KnownHostsViewModel(VaultViewModel vault)
+    /// <param name="vault">Where the pins, the reload and the withdrawal all actually live.</param>
+    /// <param name="onBack">
+    /// What the v5c header's own back arrow does — a delegate rather than a reference up to
+    /// <c>MainWindowViewModel</c>, on the same reasoning <c>ImportViewModel</c>'s own <c>onCancel</c> is one:
+    /// this type has no business knowing <c>ShellScreen</c> exists. Null in a layout test that builds this
+    /// directly makes the button a no-op rather than a crash.
+    /// </param>
+    internal KnownHostsViewModel(VaultViewModel vault, Action? onBack = null)
     {
         this.vault = vault;
+        this.onBack = onBack;
 
         // The vault rebuilds this list on every reload and every sync pass, and a screen showing a stale
         // copy of a trust decision is the one kind of staleness that matters here.
@@ -155,6 +164,14 @@ internal sealed partial class KnownHostsViewModel : ObservableObject
 
     internal bool HasPins => Shown.Any();
 
+    /// <summary>
+    /// How many approved host keys this machine can see, before the filter box narrows the table — the v5c
+    /// header's own count chip. Unfiltered, on the same reasoning <see cref="Summary"/> reads off
+    /// <see cref="Shown"/> rather than <see cref="VisiblePins"/>: it is a fact about the list, not about
+    /// whatever somebody last typed into the filter.
+    /// </summary>
+    internal int Count => Shown.Count();
+
     internal bool HasVisiblePins => VisiblePins.Count > 0;
 
     internal bool HasSelection => Selected is not null;
@@ -218,6 +235,22 @@ internal sealed partial class KnownHostsViewModel : ObservableObject
         await vault.ForgetPinCommand.ExecuteAsync(null).ConfigureAwait(true);
     }
 
+    /// <summary>Puts the selected pin's fingerprint on the clipboard. Forwarded, like <see cref="ForgetSelectedAsync"/>.</summary>
+    [RelayCommand]
+    private async Task CopyFingerprintAsync()
+    {
+        if (Selected is null)
+        {
+            return;
+        }
+
+        await vault.CopyPinFingerprintCommand.ExecuteAsync(null).ConfigureAwait(true);
+    }
+
+    /// <summary>The header's own back arrow: to the Keychain screen this list was pulled out of.</summary>
+    [RelayCommand]
+    private void Back() => onBack?.Invoke();
+
     internal void Detach() => vault.KnownHostPins.CollectionChanged -= OnPinsChanged;
 
     partial void OnFilterChanged(string value) => Rebuild();
@@ -247,6 +280,7 @@ internal sealed partial class KnownHostsViewModel : ObservableObject
         Selected = VisiblePins.FirstOrDefault(pin => pin.EntityId == selectedId);
 
         OnPropertyChanged(nameof(HasPins));
+        OnPropertyChanged(nameof(Count));
         OnPropertyChanged(nameof(HasVisiblePins));
         OnPropertyChanged(nameof(Summary));
         OnPropertyChanged(nameof(EmptyMessage));