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, 117 insertions, 0 deletions

diff --git a/cmake/DemoCodegen.cmake b/cmake/DemoCodegen.cmake
new file mode 100644
index 0000000..6c56cbd
--- /dev/null
+++ b/cmake/DemoCodegen.cmake
@@ -0,0 +1,117 @@
+# Code Generation Module
+# Asset packing, timeline compilation, and music compilation
+
+# =============================================================================
+# Helper Functions
+# =============================================================================
+
+# Helper to parse asset list and extract individual file paths
+function(parse_asset_list INPUT_TXT OUT_FILE_LIST)
+    set(ASSET_FILES "")
+    if(EXISTS ${INPUT_TXT})
+        # Get directory of INPUT_TXT for relative path resolution
+        get_filename_component(INPUT_DIR ${INPUT_TXT} DIRECTORY)
+
+        file(STRINGS ${INPUT_TXT} LINES)
+        foreach(LINE ${LINES})
+            # Skip comments and empty lines
+            string(STRIP "${LINE}" LINE)
+            if(NOT LINE MATCHES "^#" AND NOT LINE STREQUAL "")
+                # Extract filename (third field: ASSET_NAME, COMPRESSION, FILENAME, DESC)
+                string(REGEX REPLACE "^[^,]+,[^,]+,[ ]*([^,]+).*" "\\1" FILENAME "${LINE}")
+                string(STRIP "${FILENAME}" FILENAME)
+
+                # Try workspace-relative path first
+                set(FULL_PATH "${INPUT_DIR}/${FILENAME}")
+                if(NOT EXISTS ${FULL_PATH})
+                    # Fall back to legacy path for compatibility
+                    set(FULL_PATH "${CMAKE_CURRENT_SOURCE_DIR}/assets/final/${FILENAME}")
+                endif()
+
+                if(EXISTS ${FULL_PATH})
+                    list(APPEND ASSET_FILES ${FULL_PATH})
+                endif()
+            endif()
+        endforeach()
+    endif()
+    set(${OUT_FILE_LIST} ${ASSET_FILES} PARENT_SCOPE)
+endfunction()
+
+# Pack assets for demo (output to src/generated/)
+function(pack_assets NAME INPUT_TXT HEADER_VAR DATA_CC_VAR TARGET_NAME)
+    set(OUT_H ${CMAKE_CURRENT_SOURCE_DIR}/src/generated/${NAME}.h)
+    set(OUT_CC ${CMAKE_CURRENT_SOURCE_DIR}/src/generated/${NAME}_data.cc)
+
+    # Parse asset list to get individual file dependencies
+    parse_asset_list(${INPUT_TXT} ASSET_FILE_DEPS)
+
+    add_custom_command(
+        OUTPUT ${OUT_H} ${OUT_CC}
+        COMMAND ${CMAKE_COMMAND} -E make_directory ${CMAKE_CURRENT_SOURCE_DIR}/src/generated
+        COMMAND ${ASSET_PACKER_CMD} ${INPUT_TXT} ${OUT_H} ${OUT_CC}
+        DEPENDS ${ASSET_PACKER_DEPENDS} ${INPUT_TXT} ${ASSET_FILE_DEPS}
+        COMMENT "Generating assets for ${NAME}..."
+    )
+    set(${HEADER_VAR} ${OUT_H} PARENT_SCOPE)
+    set(${DATA_CC_VAR} ${OUT_CC} PARENT_SCOPE)
+    add_custom_target(${TARGET_NAME} DEPENDS ${OUT_H} ${OUT_CC})
+endfunction()
+
+# Pack test assets (output to build/src/generated_test/)
+function(pack_test_assets NAME INPUT_TXT HEADER_VAR DATA_CC_VAR TARGET_NAME)
+    set(OUT_H ${CMAKE_CURRENT_BINARY_DIR}/src/generated_test/${NAME}.h)
+    set(OUT_CC ${CMAKE_CURRENT_BINARY_DIR}/src/generated_test/${NAME}_data.cc)
+
+    # Parse asset list to get individual file dependencies
+    parse_asset_list(${INPUT_TXT} ASSET_FILE_DEPS)
+
+    add_custom_command(
+        OUTPUT ${OUT_H} ${OUT_CC}
+        COMMAND ${CMAKE_COMMAND} -E make_directory ${CMAKE_CURRENT_BINARY_DIR}/src/generated_test
+        COMMAND ${ASSET_PACKER_CMD} ${INPUT_TXT} ${OUT_H} ${OUT_CC}
+        DEPENDS ${ASSET_PACKER_DEPENDS} ${INPUT_TXT} ${ASSET_FILE_DEPS}
+        COMMENT "Generating assets for test ${NAME}..."
+    )
+    set(${HEADER_VAR} ${OUT_H} PARENT_SCOPE)
+    set(${DATA_CC_VAR} ${OUT_CC} PARENT_SCOPE)
+    add_custom_target(${TARGET_NAME} DEPENDS ${OUT_H} ${OUT_CC})
+endfunction()
+
+# =============================================================================
+# Generation Targets
+# =============================================================================
+
+# Timeline compilation
+set(DEMO_SEQ_PATH ${WORKSPACE_TIMELINE})
+set(GENERATED_TIMELINE_CC ${CMAKE_CURRENT_SOURCE_DIR}/src/generated/timeline.cc)
+add_custom_command(
+    OUTPUT ${GENERATED_TIMELINE_CC}
+    COMMAND ${CMAKE_COMMAND} -E make_directory ${CMAKE_CURRENT_SOURCE_DIR}/src/generated
+    COMMAND ${SEQ_COMPILER_CMD} ${DEMO_SEQ_PATH} ${GENERATED_TIMELINE_CC}
+    DEPENDS ${SEQ_COMPILER_DEPENDS} ${DEMO_SEQ_PATH}
+            src/gpu/demo_effects.h
+    COMMENT "Compiling demo sequence from workspace ${DEMO_WORKSPACE}..."
+)
+add_custom_target(generate_timeline ALL DEPENDS ${GENERATED_TIMELINE_CC})
+
+# Music compilation
+set(TRACKER_MUSIC_PATH ${WORKSPACE_MUSIC})
+set(GENERATED_MUSIC_DATA_CC ${CMAKE_CURRENT_SOURCE_DIR}/src/generated/music_data.cc)
+add_custom_command(
+    OUTPUT ${GENERATED_MUSIC_DATA_CC}
+    COMMAND ${CMAKE_COMMAND} -E make_directory ${CMAKE_CURRENT_SOURCE_DIR}/src/generated
+    COMMAND ${TRACKER_COMPILER_FINAL_CMD} ${TRACKER_MUSIC_PATH} ${GENERATED_MUSIC_DATA_CC}
+    DEPENDS ${TRACKER_COMPILER_FINAL_DEPENDS} ${TRACKER_MUSIC_PATH} tracker_compiler_host
+    COMMENT "Compiling tracker music from workspace ${DEMO_WORKSPACE}..."
+)
+add_custom_target(generate_tracker_music ALL DEPENDS ${GENERATED_MUSIC_DATA_CC})
+
+# Asset packing
+pack_assets(assets ${WORKSPACE_ASSETS} GEN_DEMO_H GEN_DEMO_CC generate_demo_assets)
+pack_test_assets(test_assets ${CMAKE_CURRENT_SOURCE_DIR}/assets/final/test_assets_list.txt GEN_TEST_H GEN_TEST_CC generate_test_assets)
+
+# Mark generated files so CMake always checks if they need rebuilding
+set_source_files_properties(${GEN_DEMO_H} ${GEN_DEMO_CC} PROPERTIES GENERATED TRUE)
+set_source_files_properties(${GEN_TEST_H} ${GEN_TEST_CC} PROPERTIES GENERATED TRUE)
+set_source_files_properties(${GENERATED_TIMELINE_CC} PROPERTIES GENERATED TRUE)
+set_source_files_properties(${GENERATED_MUSIC_DATA_CC} PROPERTIES GENERATED TRUE)