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, 48 insertions, 0 deletions

diff --git a/cmake/DemoTools.cmake b/cmake/DemoTools.cmake
new file mode 100644
index 0000000..8c589f1
--- /dev/null
+++ b/cmake/DemoTools.cmake
@@ -0,0 +1,48 @@
+# Build Tools Setup
+# Configures asset_packer, seq_compiler, and tracker_compiler
+
+# Asset packer tool
+if(DEFINED ASSET_PACKER_PATH)
+    set(ASSET_PACKER_CMD ${ASSET_PACKER_PATH})
+    set(ASSET_PACKER_DEPENDS ${ASSET_PACKER_PATH})
+else()
+    add_executable(asset_packer tools/asset_packer.cc)
+    target_link_libraries(asset_packer PRIVATE procedural)
+    target_include_directories(asset_packer PRIVATE third_party)
+    set(ASSET_PACKER_CMD $<TARGET_FILE:asset_packer>)
+    set(ASSET_PACKER_DEPENDS asset_packer)
+endif()
+
+# Sequence compiler tool
+if(DEFINED SEQ_COMPILER_PATH)
+    set(SEQ_COMPILER_CMD ${SEQ_COMPILER_PATH})
+    set(SEQ_COMPILER_DEPENDS ${SEQ_COMPILER_PATH})
+else()
+    add_executable(seq_compiler tools/seq_compiler.cc)
+    set(SEQ_COMPILER_CMD $<TARGET_FILE:seq_compiler>)
+    set(SEQ_COMPILER_DEPENDS seq_compiler)
+endif()
+
+# Tracker compiler tool
+if(DEFINED TRACKER_COMPILER_PATH)
+    set(TRACKER_COMPILER_CMD ${TRACKER_COMPILER_PATH})
+    set(TRACKER_COMPILER_DEPENDS ${TRACKER_COMPILER_PATH})
+else()
+    add_executable(tracker_compiler tools/tracker_compiler.cc)
+    set(TRACKER_COMPILER_CMD $<TARGET_FILE:tracker_compiler>)
+    set(TRACKER_COMPILER_DEPENDS tracker_compiler)
+endif()
+
+# Always build a host-native tracker_compiler for code generation purposes
+add_executable(tracker_compiler_host tools/tracker_compiler.cc)
+set_target_properties(tracker_compiler_host PROPERTIES
+    RUNTIME_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/tools_host")
+
+# Determine which tracker compiler to use for code generation
+if(DEMO_CROSS_COMPILE_WIN32)
+    set(TRACKER_COMPILER_FINAL_CMD "${CMAKE_SOURCE_DIR}/build_native/tools_host/tracker_compiler_host")
+    set(TRACKER_COMPILER_FINAL_DEPENDS tracker_compiler_host)
+else()
+    set(TRACKER_COMPILER_FINAL_CMD ${TRACKER_COMPILER_CMD})
+    set(TRACKER_COMPILER_FINAL_DEPENDS ${TRACKER_COMPILER_DEPENDS})
+endif()