重构平台条件编译，剥离 LightGame 调试内容到 Debug 配置

- 把 USE_FRAMEBUFFER 替换为 TARGET_IMX / TARGET_PC 双正向互斥宏，由 CMake 选项 TARGET_IMX 推导，代码层只用 #ifdef 正向判断
- 新增 IMX6U_DEBUG 宏，通过 $<$<CONFIG:Debug>:...> 只在 Debug 构建中注入
- LightGame 关卡编辑器（LevelEditor + ImGui）改为仅 PC + Debug 编入，Release 不参与编译
- LightGame draw_debug、debug_mode_、--debug 命令行、[INFO] 启动日志全部用 IMX6U_DEBUG 门控，Release 二进制中完全消失
- [WARN] 硬件初始化失败提示保留在 Release，作为现场诊断信息
- README、APP_AND_CORE_ARCHITECTURE、Game README 同步新宏命名，并新增「构建类型与调试开关」小节

CMakeLists.txt

@@ -9,7 +9,12 @@ if(NOT CMAKE_CONFIGURATION_TYPES AND NOT CMAKE_BUILD_TYPE)
     set(CMAKE_BUILD_TYPE Release CACHE STRING "Build type" FORCE)
 endif()
 
-option(USE_FRAMEBUFFER "Use Linux framebuffer instead of SDL2" OFF)
+option(TARGET_IMX "Build for IMX6U target board (framebuffer + Alsa + Evdev). OFF builds for PC (SDL2)." OFF)
+if(TARGET_IMX)
+    set(TARGET_PC OFF)
+else()
+    set(TARGET_PC ON)
+endif()
 
 set(CORE_SOURCES
     src/Core/Asset/ObjLoader.cpp
@@ -29,7 +34,7 @@ set(CORE_SOURCES
     src/Core/Shading/BlinnPhongShader.cpp
 )
 
-if(USE_FRAMEBUFFER)
+if(TARGET_IMX)
     list(APPEND CORE_SOURCES
         src/Core/Platform/FBDisplay.cpp
         src/Core/Platform/Ap3216cPhotoSensor.cpp
@@ -60,7 +65,7 @@ set(CORE_INCLUDE_DIRS
     assets/sprite
 )
 
-if(NOT USE_FRAMEBUFFER)
+if(NOT TARGET_IMX)
     list(APPEND CORE_SOURCES
         third_party/imgui/imgui.cpp
         third_party/imgui/imgui_demo.cpp
@@ -76,11 +81,15 @@ endif()
 add_library(imx6u_core STATIC ${CORE_SOURCES})
 target_include_directories(imx6u_core PUBLIC ${CORE_INCLUDE_DIRS})
 
-if(USE_FRAMEBUFFER)
-    target_compile_definitions(imx6u_core PUBLIC USE_FRAMEBUFFER)
+if(TARGET_IMX)
+    target_compile_definitions(imx6u_core PUBLIC TARGET_IMX)
+else()
+    target_compile_definitions(imx6u_core PUBLIC TARGET_PC)
 endif()
 
-if(USE_FRAMEBUFFER)
+target_compile_definitions(imx6u_core PUBLIC $<$<CONFIG:Debug>:IMX6U_DEBUG>)
+
+if(TARGET_IMX)
 else()
     if(WIN32)
         if(CMAKE_SIZEOF_VOID_P EQUAL 8)
@@ -136,7 +145,7 @@ function(imx6u_configure_app_target target_name)
         )
     endif()
 
-    if(WIN32 AND NOT USE_FRAMEBUFFER)
+    if(WIN32 AND NOT TARGET_IMX)
         add_custom_command(TARGET ${target_name} POST_BUILD
             COMMAND ${CMAKE_COMMAND} -E copy_if_different
             "${SDL2_DLL}"
@@ -154,7 +163,7 @@ add_subdirectory(src/Apps/Game)
 add_subdirectory(src/Apps/Demo)
 add_subdirectory(src/Apps/LightGame)
 
-if(BUILD_TESTING AND NOT USE_FRAMEBUFFER)
+if(BUILD_TESTING AND NOT TARGET_IMX)
     add_executable(render_pipeline_tests
         tests/render_pipeline_tests.cpp
     )