Add wxPrinting test app and verify printing infrastructure works

- Create print_test standalone app testing wxPrintout, wxPrintPreview,
  wxPrinter, and browser print via window.print()
- Add 8 E2E tests for printing functionality (all pass)
- Update WHATWORKS.md: printing now works, 127 total tests, 14 standalone apps
- Remove wxRichTextCtrl from untested (disabled, KiCad doesn't use it)

Key findings:
- Printing infrastructure works out of the box in WASM
- wxPrintout callbacks fire correctly (OnBeginPrinting, OnPrintPage, etc.)
- wxPrintPreview renders preview frame
- Browser Print triggers native print dialog via window.print()

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

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

tests/wasm-app/Makefile.wasm

@@ -80,7 +80,8 @@ all: minimal_test.html \
      $(S)/tree/tree_test.html \
      $(S)/dataview/dataview_test.html \
      $(S)/htmlwin/htmlwin_test.html \
-     $(S)/stc/stc_test.html
+     $(S)/stc/stc_test.html \
+     $(S)/print/print_test.html
 
 # Main test app (uses GL)
 minimal_test.o: minimal_test.cpp
@@ -180,6 +181,13 @@ $(S)/stc/stc_test.o: $(S)/stc/stc_test.cpp
 $(S)/stc/stc_test.html: $(S)/stc/stc_test.o
 	$(CXX) $< $(LDFLAGS_STC) --pre-js $(JS) --shell-file $(HTML) -o $@
 
+# Print test (no GL)
+$(S)/print/print_test.o: $(S)/print/print_test.cpp
+	$(CXX) -c $(CXXFLAGS) $< -o $@
+
+$(S)/print/print_test.html: $(S)/print/print_test.o
+	$(CXX) $< $(LDFLAGS_NOGL) --pre-js $(JS) --shell-file $(HTML) -o $@
+
 # Convenience targets
 menu: $(S)/menu/menu_test.html
 clipboard: $(S)/clipboard/clipboard_test.html
@@ -194,9 +202,10 @@ tree: $(S)/tree/tree_test.html
 dataview: $(S)/dataview/dataview_test.html
 htmlwin: $(S)/htmlwin/htmlwin_test.html
 stc: $(S)/stc/stc_test.html
+print: $(S)/print/print_test.html
 
 clean:
 	rm -f minimal_test.o minimal_test.html minimal_test.js minimal_test.wasm
 	rm -f $(S)/*/*.o $(S)/*/*.html $(S)/*/*.js $(S)/*/*.wasm
 
-.PHONY: all clean menu clipboard filedialog layout aui toolbar grid dialog timer tree dataview htmlwin stc
+.PHONY: all clean menu clipboard filedialog layout aui toolbar grid dialog timer tree dataview htmlwin stc print