docs: add simulator mode and test-apps flags to DESKTOP-DESIGNER.md

docs/DESKTOP-DESIGNER.md

@@ -24,11 +24,40 @@ The desktop designer (`designer/`) provides rapid UI development with:
 ## Command Line Options
 
 ```
+--simulator         Enable simulator mode (shows home screen with third-party apps)
+--test-apps <path>  Path to test-apps directory (default: auto-detect)
+--assets <path>     Set assets directory (default: derived from document)
 --log <path>        Write logs to file
 --hierarchy <path>  Dump UI hierarchy JSON each frame
 --dump              Single-shot dump mode (screenshot + hierarchy)
 --record <path>     Enable recording mode (F5 to start/stop)
 --playback <path>   Play back recorded actions from JSON
+--resolution WxH    Set window resolution (default: 540x960)
+```
+
+## Running the Designer
+
+### Simulator Mode (Recommended for Testing Apps)
+
+To run the designer with third-party test apps visible:
+
+```bash
+cd MosisService
+./designer/build/Release/mosis-designer.exe --simulator --test-apps test-apps
+```
+
+This will:
+- Load the home screen from `src/main/assets/apps/home/home.rml`
+- Scan `test-apps/` for apps with valid `manifest.json`
+- Display discovered apps in the home screen grid
+- Enable the `mosis.apps` Lua API for app launching
+
+### Direct Document Mode
+
+To load a specific RML document directly:
+
+```bash
+./designer/build/Release/mosis-designer.exe path/to/document.rml
 ```
 
 ## Keyboard Controls