Fix wxWidgets WASM rendering and add comprehensive tests

- Update wxwidgets submodule with bitmap, template, and listbox fixes
- Add pcre2 include path to build script
- Add comprehensive UI interaction test covering all tabs
- Update test app with full control demonstration
- Add Makefile.wasm with HEAP exports for Emscripten
- Fix .gitignore to not ignore Makefile.wasm

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

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

.gitignore

@@ -18,8 +18,9 @@ cmake-build-*/
 *.dylib
 *.dll
 
-# WebAssembly output
+# WebAssembly output (but not Makefiles that end in .wasm)
 *.wasm
+!Makefile.wasm
 *.js.map
 
 # macOS
@@ -36,5 +37,5 @@ wxwidgets-clean/
 /tests/playwright-report/
 /tests/test-results/
 /tests/wasm-app/*.js
-/tests/wasm-app/*.wasm
+/tests/wasm-app/minimal_test.wasm
 /temp/