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/test_rawloader.cpp

@@ -0,0 +1,102 @@
+#include <gtest/gtest.h>
+
+#include "converter/rawloader/RawLoader.h"
+
+#include <filesystem>
+
+using namespace photoconv;
+
+#ifndef TEST_DATA_DIR
+#define TEST_DATA_DIR "import"
+#endif
+
+static const std::filesystem::path kTestDataDir{TEST_DATA_DIR};
+
+// ──────────────────────────────────────────────
+// File validation tests
+// ──────────────────────────────────────────────
+
+TEST(RawLoaderTest, RejectsNonexistentFile) {
+    RawLoader loader;
+    auto result = loader.load("/nonexistent/file.arw");
+
+    ASSERT_FALSE(result.has_value());
+    EXPECT_EQ(result.error().code, ErrorCode::FileNotFound);
+}
+
+TEST(RawLoaderTest, RejectsUnsupportedFormat) {
+    // Create a temporary file with unsupported extension
+    auto temp = std::filesystem::temp_directory_path() / "test.xyz";
+    {
+        std::ofstream f(temp);
+        f << "dummy";
+    }
+
+    RawLoader loader;
+    auto result = loader.load(temp);
+
+    ASSERT_FALSE(result.has_value());
+    EXPECT_EQ(result.error().code, ErrorCode::UnsupportedFormat);
+
+    std::filesystem::remove(temp);
+}
+
+// ──────────────────────────────────────────────
+// RAW loading integration tests (require test data)
+// ──────────────────────────────────────────────
+
+TEST(RawLoaderTest, LoadsArwFile) {
+    auto arw_path = kTestDataDir / "DSC09246.ARW";
+    if (!std::filesystem::exists(arw_path)) {
+        GTEST_SKIP() << "Test data not available: " << arw_path;
+    }
+
+    RawLoader loader;
+    auto result = loader.load(arw_path);
+
+    ASSERT_TRUE(result.has_value()) << result.error().format();
+
+    // Verify 16-bit BGR output
+    EXPECT_EQ(result->rgb.type(), CV_16UC3);
+    EXPECT_GT(result->rgb.cols, 0);
+    EXPECT_GT(result->rgb.rows, 0);
+
+    // Verify metadata was populated
+    EXPECT_FALSE(result->metadata.camera_make.empty());
+    EXPECT_GT(result->metadata.raw_width, 0);
+    EXPECT_GT(result->metadata.raw_height, 0);
+}
+
+TEST(RawLoaderTest, MetadataContainsSonyMake) {
+    auto arw_path = kTestDataDir / "DSC09246.ARW";
+    if (!std::filesystem::exists(arw_path)) {
+        GTEST_SKIP() << "Test data not available: " << arw_path;
+    }
+
+    RawLoader loader;
+    auto result = loader.load(arw_path);
+    ASSERT_TRUE(result.has_value());
+
+    // Sony ARW files should have "Sony" as make
+    EXPECT_EQ(result->metadata.camera_make, "Sony");
+}
+
+// ──────────────────────────────────────────────
+// Pixel integrity tests
+// ──────────────────────────────────────────────
+
+TEST(RawLoaderTest, OutputIsNonTrivial) {
+    auto arw_path = kTestDataDir / "DSC09246.ARW";
+    if (!std::filesystem::exists(arw_path)) {
+        GTEST_SKIP() << "Test data not available: " << arw_path;
+    }
+
+    RawLoader loader;
+    auto result = loader.load(arw_path);
+    ASSERT_TRUE(result.has_value());
+
+    // Image should have non-zero content (not all black or all white)
+    cv::Scalar mean_val = cv::mean(result->rgb);
+    EXPECT_GT(mean_val[0], 100.0);   // Not all black
+    EXPECT_LT(mean_val[0], 65000.0); // Not all white
+}