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/README.md

@@ -0,0 +1,74 @@
+# WASM Compatibility Layer
+
+This directory contains WASM-specific implementations that allow KiCad to run in a web browser **without modifying KiCad's source code**.
+
+## Principle
+
+Instead of patching KiCad source files, we:
+1. Override include paths to use our headers first
+2. Provide alternative implementations for platform-specific code
+3. Link our libraries instead of system libraries
+
+## Directory Structure
+
+```
+wasm/
+├── CMakeLists.txt          # Master CMake for compatibility layer
+├── README.md               # This file
+├── kiplatform/             # Platform abstraction implementations
+│   ├── CMakeLists.txt
+│   ├── app.cpp             # App lifecycle (paths, startup)
+│   ├── drivers.cpp         # GPU detection (returns "WebGL")
+│   ├── environment.cpp     # Environment variables (localStorage)
+│   ├── io.cpp              # File I/O (WASM virtual filesystem)
+│   ├── policy.cpp          # Security policy (always permissive)
+│   ├── secrets.cpp         # Credential storage (localStorage)
+│   ├── sysinfo.cpp         # System information
+│   └── printing.cpp        # Print support (browser print())
+├── libcontext/             # Coroutine/fiber implementation
+│   ├── CMakeLists.txt
+│   └── fcontext_wasm.cpp   # Emscripten Asyncify fibers
+├── shims/                  # Header overrides
+│   └── *.h                 # Headers that redirect to our impls
+└── config/                 # Build configuration
+    ├── kicad_wasm_config.h # Version and feature config
+    └── setup.h             # Platform setup
+```
+
+## How It Works
+
+### Include Path Override
+
+When building KiCad for WASM, we add our directories first in the include path:
+
+```bash
+-I$PROJECT_ROOT/wasm/shims
+-I$PROJECT_ROOT/wasm/kiplatform
+-I$PROJECT_ROOT/stubs/include
+```
+
+This means when KiCad includes `<kiplatform/app.h>`, it finds our version first.
+
+### Library Override
+
+We build `libkiplatform_wasm.a` and link it instead of the native kiplatform:
+
+```bash
+-L$BUILD_ROOT/wasm -lkiplatform_wasm
+```
+
+### CMake Integration
+
+The main KiCad build is configured to find our implementations:
+
+```cmake
+-DCMAKE_MODULE_PATH="$PROJECT_ROOT/cmake"
+-DKIPLATFORM_LIBRARY="$BUILD_ROOT/wasm/libkiplatform_wasm.a"
+```
+
+## Adding New Implementations
+
+1. Create the implementation file in the appropriate directory
+2. Add it to the CMakeLists.txt
+3. Ensure the header interface matches KiCad's expected interface
+4. Test with a minimal build before full integration