Add standalone test apps and Playwright specs for wxWidgets WASM

- Add 10 standalone test apps for isolated component testing:
  - menu, toolbar, layout, aui, clipboard, filedialog, grid
  - dialog, timer, tree (3 new)
- Add 12 Playwright e2e test specs for automated testing
- Update Makefile with GL/non-GL build configurations
- Update build script to list all standalone tests
- Add WHATWORKS.md documenting KiCad wxWidgets coverage
- Update .gitignore for build artifacts

Test results:
- 79 Playwright tests pass
- wxGrid crashes (memory access out of bounds)
- wxTreeCtrl crashes (similar issue)
- wxDialog/wxMessageBox events fire but no visual popup

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

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

tests/wasm-app/standalone/layout/layout_test.cpp

@@ -0,0 +1,142 @@
+// Layout Test - Tests wxSplitterWindow and wxScrolledWindow in WASM
+// KiCad uses splitters and scrolled windows extensively
+
+#include "wx/wxprec.h"
+
+#ifndef WX_PRECOMP
+    #include "wx/wx.h"
+#endif
+
+#include "wx/splitter.h"
+#include "wx/scrolwin.h"
+
+#ifdef __EMSCRIPTEN__
+#include <emscripten/emscripten.h>
+#endif
+
+class LayoutTestApp : public wxApp
+{
+public:
+    virtual bool OnInit() override;
+};
+
+class LayoutTestFrame : public wxFrame
+{
+public:
+    LayoutTestFrame();
+
+private:
+    wxSplitterWindow* m_splitter;
+    wxScrolledWindow* m_scrollLeft;
+    wxScrolledWindow* m_scrollRight;
+    wxTextCtrl* m_log;
+
+    void LogEvent(const wxString& msg);
+    void OnSplitterSashPosChanged(wxSplitterEvent& evt);
+    void OnScrollWin(wxScrollWinEvent& evt);
+
+    wxDECLARE_EVENT_TABLE();
+};
+
+wxBEGIN_EVENT_TABLE(LayoutTestFrame, wxFrame)
+    EVT_SPLITTER_SASH_POS_CHANGED(wxID_ANY, LayoutTestFrame::OnSplitterSashPosChanged)
+wxEND_EVENT_TABLE()
+
+wxIMPLEMENT_APP(LayoutTestApp);
+
+bool LayoutTestApp::OnInit()
+{
+    if (!wxApp::OnInit())
+        return false;
+
+    LayoutTestFrame* frame = new LayoutTestFrame();
+    frame->Show(true);
+    return true;
+}
+
+LayoutTestFrame::LayoutTestFrame()
+    : wxFrame(nullptr, wxID_ANY, "wxSplitter/wxScrolled WASM Test",
+              wxDefaultPosition, wxSize(800, 600))
+{
+    wxBoxSizer* mainSizer = new wxBoxSizer(wxVERTICAL);
+
+    wxStaticText* desc = new wxStaticText(this, wxID_ANY,
+        "wxSplitterWindow and wxScrolledWindow Test - KiCad layout controls");
+    mainSizer->Add(desc, 0, wxALL, 5);
+
+    // Create splitter
+    m_splitter = new wxSplitterWindow(this, wxID_ANY, wxDefaultPosition,
+        wxDefaultSize, wxSP_3D | wxSP_LIVE_UPDATE);
+
+    // Left scrolled window
+    m_scrollLeft = new wxScrolledWindow(m_splitter, wxID_ANY);
+    m_scrollLeft->SetBackgroundColour(*wxLIGHT_GREY);
+    m_scrollLeft->SetScrollbars(10, 10, 100, 100);
+
+    wxBoxSizer* leftSizer = new wxBoxSizer(wxVERTICAL);
+    for (int i = 0; i < 20; i++) {
+        leftSizer->Add(new wxStaticText(m_scrollLeft, wxID_ANY,
+            wxString::Format("Left Item %d", i+1)), 0, wxALL, 5);
+    }
+    m_scrollLeft->SetSizer(leftSizer);
+
+    // Right scrolled window
+    m_scrollRight = new wxScrolledWindow(m_splitter, wxID_ANY);
+    m_scrollRight->SetBackgroundColour(*wxWHITE);
+    m_scrollRight->SetScrollbars(10, 10, 100, 100);
+
+    wxBoxSizer* rightSizer = new wxBoxSizer(wxVERTICAL);
+    for (int i = 0; i < 20; i++) {
+        rightSizer->Add(new wxStaticText(m_scrollRight, wxID_ANY,
+            wxString::Format("Right Item %d", i+1)), 0, wxALL, 5);
+    }
+    m_scrollRight->SetSizer(rightSizer);
+
+    m_splitter->SplitVertically(m_scrollLeft, m_scrollRight, 300);
+    m_splitter->SetMinimumPaneSize(100);
+
+    mainSizer->Add(m_splitter, 1, wxEXPAND | wxALL, 5);
+
+    // Event log
+    wxStaticBoxSizer* logBox = new wxStaticBoxSizer(wxVERTICAL, this, "Event Log");
+    m_log = new wxTextCtrl(this, wxID_ANY, "",
+        wxDefaultPosition, wxSize(-1, 100), wxTE_MULTILINE | wxTE_READONLY);
+    logBox->Add(m_log, 1, wxEXPAND | wxALL, 5);
+    mainSizer->Add(logBox, 0, wxEXPAND | wxALL, 5);
+
+    SetSizer(mainSizer);
+    CreateStatusBar();
+    SetStatusText("Drag splitter sash or scroll the panes");
+
+    LogEvent("Layout test app started");
+    LogEvent("Splitter position: 300");
+
+#ifdef __EMSCRIPTEN__
+    EM_ASM({
+        console.log('[LAYOUT_TEST] wxSplitter/wxScrolled test app started successfully');
+    });
+#endif
+}
+
+void LayoutTestFrame::LogEvent(const wxString& msg)
+{
+    m_log->AppendText(msg + "\n");
+    SetStatusText(msg);
+
+#ifdef __EMSCRIPTEN__
+    EM_ASM({
+        console.log('[LAYOUT_EVENT] ' + UTF8ToString($0));
+    }, msg.c_str().AsChar());
+#endif
+}
+
+void LayoutTestFrame::OnSplitterSashPosChanged(wxSplitterEvent& evt)
+{
+    LogEvent(wxString::Format("Splitter sash moved to: %d", evt.GetSashPosition()));
+}
+
+void LayoutTestFrame::OnScrollWin(wxScrollWinEvent& evt)
+{
+    LogEvent("Scroll event");
+    evt.Skip();
+}