Add KiCad PCBnew WASM build support and documentation

Build infrastructure:
- Update build-pcbnew.sh with stub library compilation
- Update build-wxuniversal-wasm.sh with library symlinks and stubs
- Add stub libraries for libgit2 and curl (network ops via JS)
- Add WASM-specific CMake Find modules

Documentation:
- Add KICAD_WASM_BUILD.md with complete modification list
- Document 68 KiCad files modified for WASM support
- Document disabled features and reasons
- Document stub libraries and wxWidgets changes

Submodule updates:
- kicad: Add WASM/Emscripten build support (wasm-port branch)
- wxwidgets: Add KiCad compatibility fixes

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

wasm/cmake/FindPythonLibs.cmake

@@ -0,0 +1,45 @@
+# FindPythonLibs.cmake - Stub for WASM builds
+# Python libraries are not available/needed for WASM builds (no Python scripting)
+# We provide stub values so CMake configuration succeeds
+
+if(EMSCRIPTEN)
+    message(STATUS "Python libraries stubbed for WASM build (Python scripting disabled)")
+
+    # Find the Python interpreter first (we need it for some build scripts)
+    find_program(PYTHON_EXECUTABLE NAMES python3 python)
+
+    if(PYTHON_EXECUTABLE)
+        # Get Python version
+        execute_process(
+            COMMAND "${PYTHON_EXECUTABLE}" -c "import sys; print(f'{sys.version_info.major}.{sys.version_info.minor}')"
+            OUTPUT_VARIABLE PYTHON_VERSION_STRING
+            OUTPUT_STRIP_TRAILING_WHITESPACE
+        )
+        string(REPLACE "." ";" VERSION_LIST "${PYTHON_VERSION_STRING}")
+        list(GET VERSION_LIST 0 PYTHON_VERSION_MAJOR)
+        list(GET VERSION_LIST 1 PYTHON_VERSION_MINOR)
+    else()
+        set(PYTHON_VERSION_MAJOR "3")
+        set(PYTHON_VERSION_MINOR "10")
+        set(PYTHON_VERSION_STRING "3.10")
+    endif()
+
+    # Set variables to indicate PythonLibs is "found" (stubbed)
+    set(PYTHONLIBS_FOUND TRUE)
+    set(PythonLibs_FOUND TRUE)
+
+    # Provide stub values - the actual libraries won't be linked
+    set(PYTHON_LIBRARIES "")
+    set(PYTHON_INCLUDE_DIRS "/usr/include/python${PYTHON_VERSION_STRING}")
+    set(PYTHON_INCLUDE_DIR "${PYTHON_INCLUDE_DIRS}")
+    set(PYTHON_LIBRARY "")
+
+    mark_as_advanced(
+        PYTHON_LIBRARIES
+        PYTHON_INCLUDE_DIRS
+        PYTHON_LIBRARY
+    )
+else()
+    # For non-WASM builds, use the system FindPythonLibs
+    include(${CMAKE_ROOT}/Modules/FindPythonLibs.cmake OPTIONAL)
+endif()