Add KiCad WASM build infrastructure and dependency scripts

- Add build environment setup (scripts/common/env.sh, versions.sh, functions.sh)
- Add dependency build scripts for Zstd, GLM, FreeType, HarfBuzz, Pixman, Cairo
- Add placeholder scripts for OpenCASCADE, ngspice, protobuf
- Add WASM compatibility layer (wasm/kiplatform/, wasm/libcontext/)
- Add CMake modules for KiCad WASM cross-compilation
- Add PCBnew test infrastructure (tests/kicad/)
- Add build plan documentation

Successfully tested builds: Zstd 1.5.5, GLM 0.9.9.8, FreeType 2.13.2,
HarfBuzz 8.3.0, Pixman 0.42.2, Cairo 1.18.0

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

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

scripts/deps/build-opencascade.sh

@@ -0,0 +1,96 @@
+#!/bin/bash
+# Build OpenCASCADE Technology (OCCT) for WebAssembly
+# OCCT provides 3D geometry kernel for STEP file import/export
+
+set -e
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "${SCRIPT_DIR}/../common/env.sh"
+source "${SCRIPT_DIR}/../common/versions.sh"
+source "${SCRIPT_DIR}/../common/functions.sh"
+
+OCC_DIR="${DEPS_ROOT}/opencascade-${OCC_VERSION}"
+OCC_BUILD="${BUILD_ROOT}/deps/opencascade"
+OCC_STAMP="${BUILD_ROOT}/stamps/opencascade.stamp"
+
+# Parse arguments
+CLEAN=0
+for arg in "$@"; do
+    case $arg in
+        --clean)
+            CLEAN=1
+            shift
+            ;;
+    esac
+done
+
+if [ $CLEAN -eq 1 ]; then
+    log_info "Cleaning OpenCASCADE build..."
+    rm -rf "${OCC_BUILD}" "${OCC_STAMP}"
+fi
+
+# Check if already built
+if check_stamp "${OCC_STAMP}"; then
+    log_info "OpenCASCADE already built, skipping..."
+    exit 0
+fi
+
+# Download if needed
+if [ ! -d "${OCC_DIR}" ]; then
+    log_info "Downloading OpenCASCADE ${OCC_VERSION}..."
+    mkdir -p "${DEPS_ROOT}"
+    cd "${DEPS_ROOT}"
+
+    # OpenCASCADE releases are on GitHub
+    OCC_URL="https://github.com/Open-Cascade-SAS/OCCT/archive/refs/tags/V${OCC_VERSION//./_}.tar.gz"
+    download_file "${OCC_URL}" "opencascade-${OCC_VERSION}.tar.gz"
+    tar -xzf "opencascade-${OCC_VERSION}.tar.gz"
+    mv "OCCT-V${OCC_VERSION//./_}" "opencascade-${OCC_VERSION}"
+    rm "opencascade-${OCC_VERSION}.tar.gz"
+fi
+
+log_info "Building OpenCASCADE ${OCC_VERSION} for WASM..."
+log_warn "This is a large library and may take a while..."
+
+mkdir -p "${OCC_BUILD}"
+cd "${OCC_BUILD}"
+
+# OpenCASCADE build configuration for WASM
+# Disable GUI, visualization that needs X11/OpenGL native
+# Enable core geometry and data exchange modules only
+emcmake cmake "${OCC_DIR}" \
+    -DCMAKE_BUILD_TYPE=Release \
+    -DCMAKE_INSTALL_PREFIX="${SYSROOT}" \
+    -DCMAKE_CXX_FLAGS="-pthread -O2" \
+    -DCMAKE_C_FLAGS="-pthread -O2" \
+    -DBUILD_LIBRARY_TYPE=Static \
+    -DBUILD_MODULE_ApplicationFramework=OFF \
+    -DBUILD_MODULE_Draw=OFF \
+    -DBUILD_MODULE_Visualization=OFF \
+    -DBUILD_MODULE_DETools=OFF \
+    -DBUILD_MODULE_FoundationClasses=ON \
+    -DBUILD_MODULE_ModelingData=ON \
+    -DBUILD_MODULE_ModelingAlgorithms=ON \
+    -DBUILD_MODULE_DataExchange=ON \
+    -DUSE_FREETYPE=OFF \
+    -DUSE_FREEIMAGE=OFF \
+    -DUSE_OPENVR=OFF \
+    -DUSE_FFMPEG=OFF \
+    -DUSE_TBB=OFF \
+    -DUSE_VTK=OFF \
+    -DUSE_TCL=OFF \
+    -DUSE_TK=OFF \
+    -DUSE_GLES2=OFF \
+    -DUSE_OPENGL=OFF \
+    -DUSE_D3D=OFF \
+    -DUSE_RAPIDJSON=OFF \
+    -DUSE_DRACO=OFF \
+    -DBUILD_DOC_Overview=OFF \
+    -DINSTALL_SAMPLES=OFF \
+    -DINSTALL_TEST_CASES=OFF
+
+emmake make -j${JOBS}
+emmake make install
+
+create_stamp "${OCC_STAMP}"
+log_info "OpenCASCADE build complete!"