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/CLAUDE.md

@@ -58,13 +58,25 @@ Design/         — Tokens.axaml (design tokens; merged before styles)
 | `ListSettingsModalViewModel` | Name, working dir, commit type, "manual list" flag, `VerifyCommand`, delete. Hosts the shared `AgentConfigEditorViewModel` as `Agent` (scope=List) — ⚠️ save delegates to `Agent.SaveAsync(verifyCommand)` because both land in the same `list_config` row via one `UpdateListConfig` call and would otherwise clobber each other. |
 | `WeeklyReportModalViewModel` | Range pickers default "since last standup weekday → today", cached per range. |
 | `MergeHelperSelectionModalViewModel` | "Let Claude handle it" picker → [conpty-sessions](../../docs/explore-notes/conpty-sessions.md). |
-| `UsageMonitorModalViewModel` | Opened from the usage pill (shown **before** the data loads via `BeginLoad`); gauges are **dynamic** per `UsageSnapshotDto.Limits` row, and the 5h/7d ones carry three draggable stage markers (soft/hard/gate) via `UsageGaugeBar` + the pure `UsageThresholdDrag`, plus a colour-matched legend with a `NumericUpDown` per stage → [usage-monitoring](../../docs/explore-notes/usage-monitoring.md). The **analytics** part (models/tasks/cost) comes from the external TokenTracker export, not from us: without the CLI the modal shows a hint card with an install button (gated on Node ≥ 20) instead of the totals header. Gauges, gate and throttle are unaffected by it. |
+| `UsageMonitorModalViewModel` | Opened from the usage pill (shown **before** the data loads via `BeginLoad`); gauges are **dynamic** per `UsageSnapshotDto.Limits` row, and the 5h/7d ones carry three draggable stage markers (soft/hard/gate) via `UsageGaugeBar` + the pure `UsageThresholdDrag`, plus a colour-matched legend with a `NumericUpDown` per stage → [usage-monitoring](../../docs/explore-notes/usage-monitoring.md). The **analytics** part (models/tasks/cost) comes from the external TokenTracker export, not from us: without the CLI the modal shows a hint card with an install button (gated on Node ≥ 20) instead of the totals header. Gauges, gate and throttle are unaffected by it. The modal is **display + threshold drag only** — the PowerUse switch/window/handoff % it used to host moved to Settings → Execution (`GeneralSettingsTabViewModel`), and "Refresh now" is an icon in the titlebar via `ModalShell.HeaderActions` rather than a body row. |
 
 Self-explanatory: `RepoImportModalViewModel` (bulk-create lists from git repos; already-wired
 repos disabled), `MergeModalViewModel`, `WorktreesOverviewModalViewModel`,
 `UnfinishedPlanningModalViewModel`, `LogVisualizerViewModel` (last 30 min, all levels + a
 warn/error filter), `WorkerConnectionModalViewModel`, `AboutModalViewModel`.
 
+`CheatSheetsViewModel` backs the modeless `CheatSheetsWindow` (Help → Cheat Sheets): content is
+markdown under `Assets/CheatSheets/*.md` as **EmbeddedResource** (not `AvaloniaResource` —
+`AssetLoader` throws without an initialized Avalonia app, which would make the VM unconstructible
+in tests), rendered through `MarkdownView`, with a `Topmost` pin so it can sit docked beside the
+shell. A new sheet = a new `.md` file + its key in `CheatSheetsViewModel.Keys` (+ a menu entry if
+it should be directly reachable). `MarkdownView` has no table/fenced-code support, so sheets are
+bullet lists with inline code — rendered via its opt-in `CommandRows` property, which turns a
+`` `command` — description `` bullet into a mono chip + copy button + description and wraps each
+`##` section in a collapsible `Expander` (blocks are added to the open section's panel, not to the
+host). The flag is opt-in because the other three `MarkdownView` call sites (prompt-file viewer,
+weekly report, task-description preview) render prose where copy buttons would be noise.
+
 ## Diff & Conflicts
 
 `UnifiedDiffParser` (static) + `DiffModels.cs` shared types + `DiffViewerViewModel` (one unified
@@ -106,6 +118,9 @@ There is no null→bool converter — bind
 Modals use `TaskCompletionSource` results behind the reusable `ModalShell` control — the dialog
 sets the result on save/cancel, the caller awaits the TCS.
 
+`ModalShell.HeaderActions` is the titlebar slot left of maximise/close — for a window-level action
+that should stay visible without costing a body row (currently only the usage monitor's refresh).
+
 `ModalShell` also owns the window chrome for every modal: the titlebar drag goes through
 `Window.BeginMoveDrag` (so Windows snap works — drag to the top edge to maximise; the OS only
 snaps `CanResize="True"` windows, which is the opt-in), and it insets itself by the window's