feat(ui): Cheat-Sheet-Fenster im Hilfe-Menue

Sechs Markdown-Sheets (git, Conventional Commits, Claude CLI, Claude-Config,
dotnet CLI, PowerShell) als EmbeddedResource, gerendert im modelosen, per
Topmost anpinnbaren CheatSheetsWindow. MarkdownView bekommt dafuer das Opt-in
CommandRows: `befehl` - beschreibung wird zu Mono-Chip + Copy-Button, jede
##-Sektion landet in einem Expander. Enthaelt ausserdem: Mission Control
wird beim Oeffnen aus dem Minimiert-Zustand geholt, nicht nur aktiviert.

src/ClaudeDo.Ui/ViewModels/IslandsShellViewModel.cs

@@ -515,6 +515,19 @@ public sealed partial class IslandsShellViewModel : ViewModelBase, IDisposable
         if (Dialogs is not null) await Dialogs.ShowAboutAsync(vm);
     }
 
+    // One shared VM so the sheets are parsed once and the window keeps its selection/pin
+    // across reopens; the window itself is single-instance in the dialog service.
+    private CheatSheetsViewModel? _cheatSheets;
+
+    [RelayCommand]
+    private void OpenCheatSheet(string? key)
+    {
+        if (Dialogs is null) return;
+        _cheatSheets ??= new CheatSheetsViewModel();
+        if (!string.IsNullOrEmpty(key)) _cheatSheets.Select(key);
+        Dialogs.ShowCheatSheets(_cheatSheets);
+    }
+
     [RelayCommand]
     private async Task OpenLogVisualizer()
     {

src/ClaudeDo.Ui/ViewModels/Modals/CheatSheetsViewModel.cs

@@ -0,0 +1,80 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.IO;
+using System.Linq;
+using ClaudeDo.Ui.Localization;
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+
+namespace ClaudeDo.Ui.ViewModels.Modals;
+
+/// <summary>One cheat sheet: title from the file's leading <c># </c> heading, body is the rest.</summary>
+public sealed record CheatSheet(string Key, string Title, string Body);
+
+/// <summary>
+/// Backs the non-modal cheat-sheet window (Help → Cheat Sheets). Content lives as markdown
+/// under <c>Assets/CheatSheets/*.md</c> (embedded resources) and is rendered by the existing
+/// <c>MarkdownView</c>,
+/// so a new sheet is a new file — but the key list here stays explicit to keep the order
+/// deterministic and a missing resource visible instead of silently absent.
+/// </summary>
+public partial class CheatSheetsViewModel : ViewModelBase
+{
+    private static readonly string[] Keys =
+        ["git", "conventional-commits", "claude-cli", "claude-config", "dotnet-cli", "powershell"];
+
+    public ObservableCollection<CheatSheet> Sheets { get; } = [];
+
+    [ObservableProperty]
+    private CheatSheet? _selectedSheet;
+
+    /// <summary>Keeps the window above the shell so it can sit docked at a screen edge.</summary>
+    [ObservableProperty]
+    private bool _isPinned;
+
+    public Action? CloseAction { get; set; }
+
+    public CheatSheetsViewModel()
+    {
+        foreach (var key in Keys) Sheets.Add(Load(key));
+        SelectedSheet = Sheets.FirstOrDefault();
+    }
+
+    /// <summary>Preselects a sheet by key; unknown keys keep the current selection.</summary>
+    public void Select(string key)
+    {
+        var sheet = Sheets.FirstOrDefault(s => s.Key == key);
+        if (sheet is not null) SelectedSheet = sheet;
+    }
+
+    [RelayCommand]
+    private void Close() => CloseAction?.Invoke();
+
+    private static CheatSheet Load(string key)
+    {
+        var assembly = typeof(CheatSheetsViewModel).Assembly;
+        // Match by suffix rather than composing the logical name from RootNamespace — the
+        // prefix is a build detail, and a rename shouldn't silently blank the sheet.
+        var name = assembly.GetManifestResourceNames()
+            .FirstOrDefault(n => n.EndsWith($".CheatSheets.{key}.md", StringComparison.Ordinal));
+        var stream = name is null ? null : assembly.GetManifestResourceStream(name);
+        if (stream is null)
+            return new CheatSheet(key, key, Loc.T("modals.cheatSheets.missing", $"{key}.md"));
+
+        using var reader = new StreamReader(stream);
+        var text = reader.ReadToEnd().Replace("\r\n", "\n");
+
+        // The window shows the title in its own selector, so strip the leading heading
+        // rather than rendering it a second time inside the body.
+        var lines = new List<string>(text.Split('\n'));
+        var title = key;
+        var first = lines.FindIndex(l => !string.IsNullOrWhiteSpace(l));
+        if (first >= 0 && lines[first].StartsWith("# ", StringComparison.Ordinal))
+        {
+            title = lines[first][2..].Trim();
+            lines.RemoveRange(0, first + 1);
+        }
+        return new CheatSheet(key, title, string.Join('\n', lines).Trim());
+    }
+}