update Unreal build script docs: add launch command

docs/GAME-ENGINES.md

@@ -23,7 +23,32 @@ MosisService provides a virtual phone that game engines can display and interact
 
 **Location**: `D:\Dev\Mosis\MosisUnreal\Plugins\MosisSDK\`
 
-### Build Commands
+### Build Script (Recommended)
+
+Use the build script for one-command builds and deployment:
+
+```batch
+cd D:\Dev\Mosis\MosisUnreal
+
+:: Build, install, and launch (default)
+build-unreal.bat
+
+:: Build APK only
+build-unreal.bat build
+
+:: Install to device only (requires prior build)
+build-unreal.bat install
+
+:: Launch app (starts MosisService first, then MosisUnreal)
+build-unreal.bat launch
+
+:: Clean build artifacts
+build-unreal.bat clean
+```
+
+The script auto-detects connected Android devices, handles APK and OBB installation, and properly sequences app launches (MosisService must start before MosisUnreal).
+
+### Manual Build Commands
 
 ```batch
 :: Windows Editor Build
@@ -272,15 +297,50 @@ adb logcat -s MosisSDK MosisTest RMLUI Vulkan
 
 Both game engines use Vulkan to import AHardwareBuffer from MosisService.
 
+### UE5 Implementation
+
+MosisUnreal uses UE5's built-in Vulkan RHI API for hardware buffer import:
+
+```cpp
+#include "IVulkanDynamicRHI.h"
+
+// Import AHardwareBuffer as Vulkan texture (zero-copy)
+IVulkanDynamicRHI* VulkanRHI = GetIVulkanDynamicRHI();
+FTextureRHIRef ImportedTexture = VulkanRHI->RHICreateTexture2DFromAndroidHardwareBuffer(Buffer);
+
+// GPU-to-GPU copy to destination texture each frame
+ENQUEUE_RENDER_COMMAND(CopyMosisTexture)(
+    [SrcTexture, DstTexture, Width, Height](FRHICommandListImmediate& RHICmdList)
+    {
+        RHICmdList.Transition(FRHITransitionInfo(SrcTexture, ERHIAccess::Unknown, ERHIAccess::CopySrc));
+        RHICmdList.Transition(FRHITransitionInfo(DstTexture, ERHIAccess::Unknown, ERHIAccess::CopyDest));
+
+        FRHICopyTextureInfo CopyInfo;
+        CopyInfo.Size = FIntVector(Width, Height, 1);
+        RHICmdList.CopyTexture(SrcTexture, DstTexture, CopyInfo);
+
+        RHICmdList.Transition(FRHITransitionInfo(DstTexture, ERHIAccess::CopyDest, ERHIAccess::SRVMask));
+    }
+);
+```
+
+**Key files:**
+- `MosisPhoneTexture.cpp` - Vulkan import and GPU copy
+- `MosisPhoneComponent.cpp` - Frame update coordination
+
 ### Required Vulkan Extensions
 
+UE5's VulkanRHI enables these automatically on Android:
+
 ```
 VK_ANDROID_external_memory_android_hardware_buffer
 VK_KHR_external_memory
 VK_KHR_dedicated_allocation
 ```
 
-### Import Pattern
+### Raw Vulkan Import Pattern (Reference)
+
+For custom implementations outside UE5:
 
 ```cpp
 // 1. Query buffer properties
@@ -299,9 +359,6 @@ VkExternalMemoryImageCreateInfo extInfo = {
     .handleTypes = VK_EXTERNAL_MEMORY_HANDLE_TYPE_ANDROID_HARDWARE_BUFFER_BIT_ANDROID
 };
 
-AHardwareBuffer_Desc desc;
-AHardwareBuffer_describe(buffer, &desc);
-
 VkImageCreateInfo imageInfo = {
     .sType = VK_STRUCTURE_TYPE_IMAGE_CREATE_INFO,
     .pNext = &extInfo,
@@ -339,10 +396,6 @@ vkAllocateMemory(device, &allocInfo, nullptr, &memory);
 vkBindImageMemory(device, image, memory, 0);
 ```
 
-### Synchronization
-
-Currently using CPU synchronization (`vkQueueWaitIdle` / `glFinish`). Future improvement: use Vulkan semaphores for GPU-GPU sync.
-
 ### Double Buffering
 
-The imported image is copied to a local texture each frame to prevent data races with MosisService rendering.
+The imported image is copied to a local texture each frame via GPU copy to prevent data races with MosisService rendering. This is a fast GPU-to-GPU blit operation.