Add reproducible build system for wxWidgets WASM port

- Add unified patch (wxwidgets-wasm.patch) for build validation
- Add scripts:
  - generate-wxwidgets-patches.sh: Extract patches from wxwidgets state
  - build-wxwidgets-wasm-clean.sh: Build from clean clone + patches
  - build-wxuniversal-wasm.sh: Build wxWidgets for WASM
- Add wxWidgets-wasm-reference submodule (ahilss/wxWidgets-wasm)
- Update .gitignore for wxwidgets-clean/ directory

Base commit: 5ff25322553c1870cf20a2e1ba6f20ed50d9fe9a

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

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

patches/wxwidgets-wasm/README.md

@@ -0,0 +1,47 @@
+# wxWidgets WASM Port Patch
+
+Single unified patch that transforms wxWidgets into a WASM-capable build.
+
+## Base Version
+
+- Repository: git@github.com:VV-EE/wxWidgets.git
+- Commit: 5ff25322553c1870cf20a2e1ba6f20ed50d9fe9a
+- Generated: 2025-11-27 14:10:12 UTC
+
+## Patch Contents
+
+This single patch includes:
+- Main wxWidgets modifications (config.sub, configure.in, headers, sources)
+- New WASM platform: src/wasm/, include/wx/wasm/
+- New build files: build/wasm/
+- WASM theme renderer: src/univ/themes/wasm.cpp
+- Submodule config.sub updates for emscripten/wasm32 support:
+  - 3rdparty/pcre/config.sub
+  - src/expat/expat/conftools/config.sub
+  - src/jpeg/config.sub
+  - src/png/config.sub
+  - src/tiff/config/config.sub
+
+## Apply Instructions
+
+```bash
+# Clone wxWidgets fork at the base commit
+git clone git@github.com:VV-EE/wxWidgets.git wxwidgets-clean
+cd wxwidgets-clean
+git checkout 5ff25322553c1870cf20a2e1ba6f20ed50d9fe9a
+git submodule update --init --recursive
+
+# Apply the unified patch
+patch -p1 < /path/to/patches/wxwidgets-wasm/wxwidgets-wasm.patch
+
+# Build
+mkdir build && cd build
+emconfigure ../configure --host=emscripten --enable-universal ...
+emmake make
+```
+
+## Verification
+
+```bash
+shasum -a 256 -c checksums.sha256
+```