Add Playwright test infrastructure for wxWidgets WASM port

- Add tests/ directory with Playwright e2e tests
- Add minimal wxWidgets WASM test application
- Add build script for test app (scripts/build-wasm-test.sh)
- Update wxWidgets submodule with WASM build fixes
- Update .gitignore for test artifacts

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

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

.gitignore

@@ -29,4 +29,12 @@ cmake-build-*/
 .emscripten_cache/
 
 # Clean clone for reproducible builds (generated by build-wxwidgets-wasm-clean.sh)
-wxwidgets-clean/
+wxwidgets-clean/
+
+# Test artifacts
+/tests/node_modules/
+/tests/playwright-report/
+/tests/test-results/
+/tests/wasm-app/*.js
+/tests/wasm-app/*.wasm
+/temp/