refactor: Modularize CMake build system into 10 specialized modules

Refactor monolithic 866-line CMakeLists.txt into 54-line orchestrator + 10 modules:
- DemoOptions.cmake - Build option declarations
- DemoConfig.cmake - Option implications and platform detection
- DemoCommon.cmake - Shared macros (conditional sources, size opts, linking)
- DemoDependencies.cmake - External library discovery (WGPU, GLFW)
- DemoSourceLists.cmake - Conditional source file lists
- DemoLibraries.cmake - Subsystem library targets
- DemoTools.cmake - Build tools (asset_packer, compilers)
- DemoCodegen.cmake - Code generation (assets, timeline, music)
- DemoExecutables.cmake - Main binaries (demo64k, test_demo)
- DemoTests.cmake - Test infrastructure (36 tests)
- Validation.cmake - Uniform buffer validation

Benefits:
- 94% reduction in main file size (866 → 54 lines)
- Conditional module inclusion (tests only parsed if DEMO_BUILD_TESTS=ON)
- Shared macros eliminate 200+ lines of repetition
- Clear separation of concerns

All 36 tests passing. All build modes verified.

Documentation: Created doc/CMAKE_MODULES.md with module architecture.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

1 files changed, 77 insertions, 0 deletions

diff --git a/cmake/DemoConfig.cmake b/cmake/DemoConfig.cmake
new file mode 100644
index 0000000..b3167c4
--- /dev/null
+++ b/cmake/DemoConfig.cmake
@@ -0,0 +1,77 @@
+# Configuration Implications and Platform Detection
+# Processes build options and sets up platform-specific definitions
+
+# Option hierarchy: ALL_OPTIONS → FINAL_STRIP → STRIP_ALL → SIZE_OPT
+if(DEMO_ALL_OPTIONS)
+    set(DEMO_SIZE_OPT ON)
+    set(DEMO_STRIP_ALL ON)
+    set(DEMO_BUILD_TESTS ON)
+    set(DEMO_BUILD_TOOLS ON)
+    # NOTE: DEMO_FINAL_STRIP is NOT included here (too dangerous for testing)
+endif()
+
+# FINAL_STRIP: Most aggressive stripping (removes ALL error checking)
+# Implies STRIP_ALL (stricter superset)
+if(DEMO_FINAL_STRIP)
+    add_definitions(-DFINAL_STRIP)
+    set(DEMO_STRIP_ALL ON)
+    message(STATUS "FINAL_STRIP enabled - all error checking will be removed")
+endif()
+
+if(DEMO_STRIP_ALL)
+    add_definitions(-DSTRIP_ALL)
+    set(DEMO_SIZE_OPT ON)
+endif()
+
+if(DEMO_STRIP_EXTERNAL_LIBS)
+    add_definitions(-DSTRIP_EXTERNAL_LIBS)
+    # Audio: Use miniaudio null backend
+    add_definitions(-DMA_ENABLE_ONLY_SPECIFIC_BACKENDS -DMA_ENABLE_NULL)
+    message(STATUS "STRIP_EXTERNAL_LIBS enabled - binary will compile but NOT run (size measurement only)")
+endif()
+
+if(DEMO_ENABLE_COVERAGE AND APPLE)
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} --coverage")
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} --coverage")
+    set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} --coverage")
+    # Coverage requires debug info
+    set(CMAKE_BUILD_TYPE Debug)
+endif()
+
+if(DEMO_ENABLE_DEBUG_LOGS)
+    add_definitions(-DDEBUG_LOG_ALL)
+endif()
+
+if(DEMO_HEADLESS)
+    add_definitions(-DDEMO_HEADLESS)
+    add_definitions(-DMA_ENABLE_ONLY_SPECIFIC_BACKENDS -DMA_ENABLE_NULL)
+    message(STATUS "DEMO_HEADLESS enabled - functional stubs (audio works, no GPU)")
+endif()
+
+# Platform-specific definitions
+if(APPLE)
+    add_definitions(-DGLFW_EXPOSE_NATIVE_COCOA)
+elseif(WIN32)
+    add_definitions(-DGLFW_EXPOSE_NATIVE_WIN32)
+elseif(UNIX)
+    if(DEFINED CMAKE_USE_WAYLAND)
+        add_definitions(-DGLFW_EXPOSE_NATIVE_WAYLAND)
+    else()
+        add_definitions(-DGLFW_EXPOSE_NATIVE_X11)
+    endif()
+endif()
+
+# Configuration summary
+message(STATUS "")
+message(STATUS "Build Configuration:")
+message(STATUS "  DEMO_SIZE_OPT:           ${DEMO_SIZE_OPT}")
+message(STATUS "  DEMO_STRIP_ALL:          ${DEMO_STRIP_ALL}")
+message(STATUS "  DEMO_FINAL_STRIP:        ${DEMO_FINAL_STRIP}")
+message(STATUS "  DEMO_STRIP_EXTERNAL_LIBS: ${DEMO_STRIP_EXTERNAL_LIBS}")
+message(STATUS "  DEMO_BUILD_TESTS:        ${DEMO_BUILD_TESTS}")
+message(STATUS "  DEMO_BUILD_TOOLS:        ${DEMO_BUILD_TOOLS}")
+message(STATUS "  DEMO_ENABLE_COVERAGE:    ${DEMO_ENABLE_COVERAGE}")
+message(STATUS "  DEMO_ENABLE_DEBUG_LOGS:  ${DEMO_ENABLE_DEBUG_LOGS}")
+message(STATUS "  DEMO_HEADLESS:           ${DEMO_HEADLESS}")
+message(STATUS "  DEMO_WORKSPACE:          ${DEMO_WORKSPACE}")
+message(STATUS "")