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-glm.sh

@@ -0,0 +1,57 @@
+#!/bin/bash
+# Install GLM headers for WebAssembly
+# GLM is a header-only math library
+
+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"
+
+GLM_DIR="${DEPS_ROOT}/glm-${GLM_VERSION}"
+GLM_STAMP="${BUILD_ROOT}/stamps/glm.stamp"
+
+# Parse arguments
+CLEAN=0
+for arg in "$@"; do
+    case $arg in
+        --clean)
+            CLEAN=1
+            shift
+            ;;
+    esac
+done
+
+if [ $CLEAN -eq 1 ]; then
+    log_info "Cleaning GLM install..."
+    rm -rf "${GLM_STAMP}"
+fi
+
+# Check if already installed
+if check_stamp "${GLM_STAMP}"; then
+    log_info "GLM already installed, skipping..."
+    exit 0
+fi
+
+# Download if needed
+if [ ! -d "${GLM_DIR}" ]; then
+    log_info "Downloading GLM ${GLM_VERSION}..."
+    mkdir -p "${DEPS_ROOT}"
+    cd "${DEPS_ROOT}"
+
+    GLM_URL="https://github.com/g-truc/glm/releases/download/${GLM_VERSION}/glm-${GLM_VERSION}.zip"
+    download_file "${GLM_URL}" "glm-${GLM_VERSION}.zip"
+    unzip -q "glm-${GLM_VERSION}.zip"
+    mv glm "glm-${GLM_VERSION}"
+    rm "glm-${GLM_VERSION}.zip"
+fi
+
+log_info "Installing GLM ${GLM_VERSION} headers..."
+
+# GLM is header-only, just copy headers
+mkdir -p "${SYSROOT}/include"
+cp -r "${GLM_DIR}/glm" "${SYSROOT}/include/"
+
+create_stamp "${GLM_STAMP}"
+log_info "GLM install complete!"