chore: initial project scaffold from architecture design

- Add CLAUDE.md with project overview, tech stack, build commands,
  architecture description, coding standards, and sample images section
- Add full directory structure: src/, docs/, tests/, import/
- Add CMakeLists.txt with C++20, OpenCV/LibRaw/Qt6 dependencies,
  converter_core static lib, optional GUI, and GTest tests
- Add architecture documentation: ARCHITECTURE.md, PIPELINE.md, MODULES.md
- Add source skeletons for all pipeline stages:
  RawLoader, Preprocessor, NegativeDetector, Inverter, ColorCorrector,
  CropProcessor, OutputWriter, Pipeline, MainWindow, CliRunner, main.cpp
- Add initial test stubs for pipeline and rawloader
- Add sample ARW files in import/ for integration testing

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/CMakeLists.txt

@@ -0,0 +1,47 @@
+find_package(GTest REQUIRED)
+
+# ──────────────────────────────────────────────
+# Pipeline unit tests
+# ──────────────────────────────────────────────
+add_executable(test_pipeline
+    test_pipeline.cpp
+)
+
+target_link_libraries(test_pipeline PRIVATE
+    converter_core
+    GTest::gtest
+    GTest::gtest_main
+)
+
+target_include_directories(test_pipeline PRIVATE
+    ${CMAKE_SOURCE_DIR}/src
+)
+
+add_test(NAME PipelineTests COMMAND test_pipeline)
+
+# ──────────────────────────────────────────────
+# RawLoader integration tests
+# ──────────────────────────────────────────────
+add_executable(test_rawloader
+    test_rawloader.cpp
+)
+
+target_link_libraries(test_rawloader PRIVATE
+    converter_core
+    GTest::gtest
+    GTest::gtest_main
+)
+
+target_include_directories(test_rawloader PRIVATE
+    ${CMAKE_SOURCE_DIR}/src
+)
+
+add_test(NAME RawLoaderTests COMMAND test_rawloader)
+
+# Make test data path available
+target_compile_definitions(test_pipeline PRIVATE
+    TEST_DATA_DIR="${CMAKE_SOURCE_DIR}/import"
+)
+target_compile_definitions(test_rawloader PRIVATE
+    TEST_DATA_DIR="${CMAKE_SOURCE_DIR}/import"
+)