[skills] Add skills to create ports and patches

.github/skills/create-port/references/cmake-patterns.md

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+# CMake Integration Patterns
+
+## Modern CMake Targets
+
+### Standard Pattern
+```cmake
+find_package(PackageName CONFIG REQUIRED)
+target_link_libraries(main PRIVATE PackageName::PackageName)
+```
+
+### Namespaced Targets
+Popular packages often use namespace prefixes:
+```cmake
+# Boost libraries
+target_link_libraries(main PRIVATE Boost::system Boost::filesystem)
+
+# Google libraries  
+target_link_libraries(main PRIVATE glog::glog)
+target_link_libraries(main PRIVATE gtest::gtest gtest::main)
+
+# Microsoft libraries
+target_link_libraries(main PRIVATE Microsoft.GSL::GSL)
+```
+
+### Header-Only Libraries
+```cmake
+find_package(nlohmann_json CONFIG REQUIRED)
+target_link_libraries(main PRIVATE nlohmann_json::nlohmann_json)
+
+# Alternative for header-only
+target_include_directories(main PRIVATE ${nlohmann_json_INCLUDE_DIRS})
+```
+
+## Component-Based Packages
+
+### Qt Components
+```cmake
+find_package(Qt6 CONFIG REQUIRED COMPONENTS Core Widgets Network)
+target_link_libraries(main PRIVATE Qt6::Core Qt6::Widgets Qt6::Network)
+```
+
+### Boost Components
+```cmake
+find_package(Boost CONFIG REQUIRED COMPONENTS system filesystem thread)
+target_link_libraries(main PRIVATE Boost::system Boost::filesystem Boost::thread)
+```
+
+### OpenCV Components
+```cmake
+find_package(OpenCV CONFIG REQUIRED COMPONENTS core imgproc imgcodecs)
+target_link_libraries(main PRIVATE opencv::opencv)
+```
+
+## Compatibility Patterns
+
+### Legacy and Modern Support
+```cmake
+# Try modern CMake config first
+find_package(PackageName CONFIG QUIET)
+if(NOT PackageName_FOUND)
+    # Fallback to FindModule
+    find_package(PackageName MODULE REQUIRED)
+    # Create modern target from legacy variables
+    add_library(PackageName::PackageName INTERFACE IMPORTED)
+    set_target_properties(PackageName::PackageName PROPERTIES
+        INTERFACE_INCLUDE_DIRECTORIES "${PackageName_INCLUDE_DIRS}"
+        INTERFACE_LINK_LIBRARIES "${PackageName_LIBRARIES}"
+    )
+endif()
+```
+
+### Unofficial Namespace
+For packages that don't provide proper CMake configs (required by vcpkg guidelines):
+```cmake
+find_package(unofficial-sqlite3 CONFIG REQUIRED)
+target_link_libraries(main PRIVATE unofficial::sqlite3)
+```
+
+### vcpkg-Created Targets
+All targets created by vcpkg ports must use the unofficial namespace:
+```cmake
+# Correct - vcpkg port creates unofficial target
+find_package(mylib CONFIG REQUIRED)
+target_link_libraries(main PRIVATE unofficial::mylib)
+
+# Avoid - don't create targets that might conflict with upstream
+# target_link_libraries(main PRIVATE mylib::mylib)
+```
+
+## Platform-Specific Integration
+
+### Windows-Only Features
+```cmake
+if(WIN32)
+    find_package(WindowsSDK CONFIG REQUIRED)
+    target_link_libraries(main PRIVATE WindowsSDK::d3d11)
+endif()
+```
+
+### Unix-Only Libraries
+```cmake
+if(UNIX)
+    find_package(X11 REQUIRED)
+    target_link_libraries(main PRIVATE ${X11_LIBRARIES})
+endif()
+```
+
+## Feature Flags in Usage
+
+### Optional Components
+```cmake
+# Basic usage
+find_package(PackageName CONFIG REQUIRED)
+target_link_libraries(main PRIVATE PackageName::core)
+
+# With optional features
+if(ENABLE_OPENSSL)
+    find_package(PackageName CONFIG REQUIRED COMPONENTS ssl)
+    target_link_libraries(main PRIVATE PackageName::ssl)
+endif()
+```
+
+### Conditional Features
+```cmake
+# Check what features are available
+find_package(PackageName CONFIG REQUIRED)
+if(TARGET PackageName::networking)
+    target_link_libraries(main PRIVATE PackageName::networking)
+    target_compile_definitions(main PRIVATE HAS_NETWORKING=1)
+endif()
+```
+
+## Best Practices for Usage Files
+
+1. **Usage files are optional** - vcpkg generates heuristic usage when find_package() is available
+2. **Only create usage files when heuristics are incorrect** - Don't create them by default
+3. **Show working minimal examples** that users can copy-paste
+4. **Show both REQUIRED and COMPONENTS usage** when applicable  
+5. **Include conditional examples** for optional features
+6. **Use modern target syntax** (`target_link_libraries` with targets)
+7. **Document any special setup** required beyond `find_package()`
+8. **Include pkg-config alternatives** when available
+9. **Show debug/release specific usage** if needed
+10. **Never include #include statements in usage files** - That's application code, not integration guidance
+
+## Common Antipatterns to Avoid
+
+❌ **Using legacy variables:**
+```cmake
+find_package(PackageName CONFIG REQUIRED)
+include_directories(${PackageName_INCLUDE_DIRS})
+link_libraries(${PackageName_LIBRARIES})
+```
+
+❌ **Hardcoded paths:**
+```cmake
+target_include_directories(main PRIVATE "C:/vcpkg/installed/x64-windows/include")
+```
+
+✅ **Use modern targets:**
+```cmake
+find_package(PackageName CONFIG REQUIRED)
+target_link_libraries(main PRIVATE PackageName::PackageName)
+```