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>

wasm/CMakeLists.txt

@@ -0,0 +1,26 @@
+# WASM Compatibility Layer for KiCad
+# This directory contains WASM-specific implementations that replace
+# platform-specific code in KiCad without modifying KiCad's source.
+
+cmake_minimum_required(VERSION 3.22)
+project(kicad_wasm_compat)
+
+# Only build for Emscripten
+if(NOT EMSCRIPTEN)
+    message(FATAL_ERROR "This project is only for Emscripten builds")
+endif()
+
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+# Include directories
+include_directories(
+    ${CMAKE_CURRENT_SOURCE_DIR}/config
+    ${CMAKE_CURRENT_SOURCE_DIR}/shims
+)
+
+# kiplatform WASM implementation
+add_subdirectory(kiplatform)
+
+# libcontext Asyncify fiber implementation
+add_subdirectory(libcontext)