feat: Week 1 complete - Linux support + IPC API prep

🎉 Major v2.0 rebuild kickoff - Week 1 accomplished!

## Highlights

### Cross-Platform Support 🌍
- ✅ Linux primary platform (Ubuntu/Debian tested)
- ✅ Windows fully supported
- ✅ macOS experimental support
- ✅ Platform-agnostic path handling (XDG spec)
- ✅ Auto-detection of KiCAD installation

### Infrastructure 🏗️
- ✅ GitHub Actions CI/CD pipeline
- ✅ Pytest framework with 20+ tests
- ✅ Pre-commit hooks (Black, MyPy, ESLint)
- ✅ Automated Linux installation script
- ✅ Enhanced npm scripts

### IPC API Migration Prep 🚀
- ✅ Comprehensive migration plan (30 pages)
- ✅ Backend abstraction layer (800+ lines)
- ✅ Factory pattern with auto-detection
- ✅ SWIG backward compatibility wrapper
- ✅ IPC backend skeleton ready

### Documentation 📚
- ✅ Updated README (Linux installation)
- ✅ CONTRIBUTING.md guide
- ✅ Linux compatibility audit
- ✅ IPC API migration plan
- ✅ Session summaries
- ✅ Platform-specific config templates

## Files Changed

- 27 files created
- ~3,000 lines of code/docs
- 8 comprehensive documentation pages
- 20+ unit tests
- 5 abstraction layer modules

## Next Steps

- Week 2: IPC API migration (project.py → component.py → routing.py)
- Migrate from deprecated SWIG to official IPC API
- JLCPCB/Digikey integration prep

🤖 Generated with Claude Code
https://claude.com/claude-code

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

tests/test_platform_helper.py

@@ -0,0 +1,172 @@
+"""
+Tests for platform_helper utility
+
+These are unit tests that work on all platforms.
+"""
+import pytest
+import platform
+from pathlib import Path
+import sys
+import os
+
+# Add parent directory to path to import utils
+sys.path.insert(0, str(Path(__file__).parent.parent / "python"))
+
+from utils.platform_helper import PlatformHelper, detect_platform
+
+
+class TestPlatformDetection:
+    """Test platform detection functions"""
+
+    def test_exactly_one_platform_detected(self):
+        """Ensure exactly one platform is detected"""
+        platforms = [
+            PlatformHelper.is_windows(),
+            PlatformHelper.is_linux(),
+            PlatformHelper.is_macos(),
+        ]
+        assert sum(platforms) == 1, "Exactly one platform should be detected"
+
+    def test_platform_name_is_valid(self):
+        """Test platform name is human-readable"""
+        name = PlatformHelper.get_platform_name()
+        assert name in ["Windows", "Linux", "macOS"], f"Unknown platform: {name}"
+
+    def test_platform_name_matches_detection(self):
+        """Ensure platform name matches detection functions"""
+        name = PlatformHelper.get_platform_name()
+        if name == "Windows":
+            assert PlatformHelper.is_windows()
+        elif name == "Linux":
+            assert PlatformHelper.is_linux()
+        elif name == "macOS":
+            assert PlatformHelper.is_macos()
+
+
+class TestPathGeneration:
+    """Test path generation functions"""
+
+    def test_config_dir_exists_after_ensure(self):
+        """Test that config directory is created"""
+        PlatformHelper.ensure_directories()
+        config_dir = PlatformHelper.get_config_dir()
+        assert config_dir.exists(), f"Config dir should exist: {config_dir}"
+        assert config_dir.is_dir(), f"Config dir should be a directory: {config_dir}"
+
+    def test_log_dir_exists_after_ensure(self):
+        """Test that log directory is created"""
+        PlatformHelper.ensure_directories()
+        log_dir = PlatformHelper.get_log_dir()
+        assert log_dir.exists(), f"Log dir should exist: {log_dir}"
+        assert log_dir.is_dir(), f"Log dir should be a directory: {log_dir}"
+
+    def test_cache_dir_exists_after_ensure(self):
+        """Test that cache directory is created"""
+        PlatformHelper.ensure_directories()
+        cache_dir = PlatformHelper.get_cache_dir()
+        assert cache_dir.exists(), f"Cache dir should exist: {cache_dir}"
+        assert cache_dir.is_dir(), f"Cache dir should be a directory: {cache_dir}"
+
+    def test_config_dir_is_platform_appropriate(self):
+        """Test that config directory follows platform conventions"""
+        config_dir = PlatformHelper.get_config_dir()
+
+        if PlatformHelper.is_linux():
+            # Should be ~/.config/kicad-mcp or $XDG_CONFIG_HOME/kicad-mcp
+            if "XDG_CONFIG_HOME" in os.environ:
+                expected = Path(os.environ["XDG_CONFIG_HOME"]) / "kicad-mcp"
+            else:
+                expected = Path.home() / ".config" / "kicad-mcp"
+            assert config_dir == expected
+
+        elif PlatformHelper.is_windows():
+            # Should be %USERPROFILE%\.kicad-mcp
+            expected = Path.home() / ".kicad-mcp"
+            assert config_dir == expected
+
+        elif PlatformHelper.is_macos():
+            # Should be ~/Library/Application Support/kicad-mcp
+            expected = Path.home() / "Library" / "Application Support" / "kicad-mcp"
+            assert config_dir == expected
+
+    def test_python_executable_is_valid(self):
+        """Test that Python executable path is valid"""
+        exe = PlatformHelper.get_python_executable()
+        assert exe.exists(), f"Python executable should exist: {exe}"
+        assert str(exe) == sys.executable
+
+    def test_kicad_library_search_paths_returns_list(self):
+        """Test that library search paths returns a list"""
+        paths = PlatformHelper.get_kicad_library_search_paths()
+        assert isinstance(paths, list)
+        assert len(paths) > 0
+        # All paths should be strings (glob patterns)
+        assert all(isinstance(p, str) for p in paths)
+
+
+class TestDetectPlatform:
+    """Test the detect_platform convenience function"""
+
+    def test_detect_platform_returns_dict(self):
+        """Test that detect_platform returns a dictionary"""
+        info = detect_platform()
+        assert isinstance(info, dict)
+
+    def test_detect_platform_has_required_keys(self):
+        """Test that detect_platform includes all required keys"""
+        info = detect_platform()
+        required_keys = [
+            "system",
+            "platform",
+            "is_windows",
+            "is_linux",
+            "is_macos",
+            "python_version",
+            "python_executable",
+            "config_dir",
+            "log_dir",
+            "cache_dir",
+            "kicad_python_paths",
+        ]
+        for key in required_keys:
+            assert key in info, f"Missing key: {key}"
+
+    def test_detect_platform_python_version_format(self):
+        """Test that Python version is in correct format"""
+        info = detect_platform()
+        version = info["python_version"]
+        # Should be like "3.12.3"
+        parts = version.split(".")
+        assert len(parts) == 3
+        assert all(p.isdigit() for p in parts)
+
+
+@pytest.mark.integration
+class TestKiCADPathDetection:
+    """Tests that require KiCAD to be installed"""
+
+    def test_kicad_python_paths_exist(self):
+        """Test that at least one KiCAD Python path exists (if KiCAD is installed)"""
+        paths = PlatformHelper.get_kicad_python_paths()
+        # This test only makes sense if KiCAD is installed
+        # In CI, KiCAD should be installed
+        if paths:
+            assert all(p.exists() for p in paths), "All returned paths should exist"
+
+    def test_can_import_pcbnew_after_adding_paths(self):
+        """Test that pcbnew can be imported after adding KiCAD paths"""
+        PlatformHelper.add_kicad_to_python_path()
+        try:
+            import pcbnew
+            # If we get here, pcbnew is available
+            assert pcbnew is not None
+            version = pcbnew.GetBuildVersion()
+            assert version is not None
+            print(f"Found KiCAD version: {version}")
+        except ImportError:
+            pytest.skip("KiCAD pcbnew module not available (KiCAD not installed)")
+
+
+if __name__ == "__main__":
+    # Run tests with pytest
+    pytest.main([__file__, "-v"])