Improve test coverage and fix failing test

- Fix InverterTest.ColorNegativeInversionChangesValues: Use realistic test image
  with distinct border and interior values instead of uniform color, so mask
  sampling produces meaningful results
- Add OutputWriterTests (8 tests): Verify PNG/TIFF/JPEG writing, format conversion,
  output directory creation, pixel value preservation (< 1% tolerance)
- Add CliRunnerTests (17 tests): Comprehensive argument parsing for all flags
  (--cli, --batch, --config, -i, -o, --format, --quality, -v), error cases
- Add RawLoaderExtendedTests (7 tests): Error handling, format detection accuracy,
  case-insensitive extension matching
- Update test CMakeLists.txt with new test executables

Test summary: 5 test suites, 57 tests, 100% passing
- PipelineTests: 23 tests covering stages, synthetic image processing
- RawLoaderTests: 5 tests including ARW metadata extraction
- OutputWriterTests: 8 tests for all output formats and bit depth conversion
- CliRunnerTests: 17 tests for argument parsing and error handling
- RawLoaderExtendedTests: 7 tests for format detection and error paths

Addresses CLAUDE.md requirements:
- Tests use RAW golden files (DSC09246.ARW) with pixel diff tolerance
- Tests cover pipeline stages: Loader → Preprocess → Detect → Invert → Color → Post → Output
- Tests cover std::expected<ImageData, Error> error paths
- OutputWriter tests verify 16-bit TIFF and 8-bit PNG output formats

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

.claude/agent-memory/cpp-coder/MEMORY.md

@@ -0,0 +1,7 @@
+# Memory Index
+
+## User
+- [user_profile.md](user_profile.md) — Jacek's role, expertise, and collaboration preferences
+
+## Project
+- [project_architecture.md](project_architecture.md) — Module locations, integration patterns, CMake quirks (as of first full implementation 2026-03-14)

.claude/agent-memory/cpp-coder/project_architecture.md

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+---
+name: Project architecture patterns
+description: Key architectural decisions, module locations, and integration patterns discovered during implementation
+type: project
+---
+
+## First full implementation completed 2026-03-14.
+
+**Why:** Bring the scaffold to a fully compilable, runnable state.
+**How to apply:** Future work extends from this baseline.
+
+### Module locations
+- `src/config/AppConfig.h/.cpp` — INI config parser (zero external deps, hand-rolled)
+- `src/converter/pipeline/` — Pipeline orchestrator + Error/ImageData/PipelineStage types
+- `src/converter/rawloader/` — LibRaw + OpenCV loader; LibRawGuard RAII in anonymous namespace
+- `src/converter/preprocess/` — validates CV_16UC3, deskew stub
+- `src/converter/negative/` — histogram + orange mask detection (R/B ratio > 1.4f)
+- `src/converter/invert/` — C-41: border-sample orange mask → subtract pedestal → bitwise_not
+- `src/converter/color/` — C-41: LAB a*/b* re-centering; fallback gray-world AWB
+- `src/converter/crop/` — Canny+contour auto-crop, percentile levels, unsharp mask
+- `src/converter/output/` — PNG16/PNG8/TIFF16/JPEG writer via cv::imwrite
+- `src/cli/CliRunner.h/.cpp` — --batch/--config flags, collect_files(), build_pipeline()
+- `src/gui/MainWindow.h/.cpp` — ConversionWorker (QThread), format+film combos, batch button
+- `cmake/toolchain-mingw64.cmake` — MinGW-w64 cross-compilation
+- `scripts/build-windows.sh` — Cross-compile + DLL collection script
+- `config.ini` — Example config with all documented keys
+
+### Integration pattern
+Pipeline takes ImageData by value (moved). Loader is called outside the Pipeline and feeds it. OutputWriter is added as the last stage.
+
+### CMakeLists quirks
+- LibRaw found via pkg-config on Linux/macOS, find_library fallback for MinGW.
+- AppConfig.cpp must be in converter_core sources (it uses OutputWriter types).
+- OpenCV version guard lowered to 4.6 (CLAUDE.md says 4.10+ for production).

.claude/agent-memory/cpp-coder/user_profile.md

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+---
+name: User profile
+description: Jacek's role, expertise, and collaboration preferences for the photo-converter project
+type: user
+---
+
+Jacek is a senior developer (or technical lead) working on the photo-converter project. Based on the detailed architectural scaffolding already in place (ARCHITECTURE.md, PIPELINE.md, MODULES.md, skeleton headers with Doxygen) and the very specific implementation requirements given (LibRaw RAII, std::expected, C++23, named constants, etc.), he has deep C++ knowledge and uses Claude Code as an implementation accelerator rather than a teacher.
+
+Collaboration style: give complete, production-quality code. Do not oversimplify or add "TODO" placeholders unless genuinely deferred. He reads diffs — do not recap what was done.