Resolve compiler warnings (C4456, C4189, C4100)

- MainWindow.McpRoutes.cpp:191 rename inner 'first' -> 'firstField' (shadowed outer 'first' from properties loop).
- MainWindow.McpRoutes.cpp:1039 remove unused 'slashPos' (path parsing fell back to stoi-on-stripped without the slash split).
- MainWindow.xaml.cpp click handler: drop unused 'imgDipX'/'imgDipY' locals (only normX/normY used downstream).
- MainWindow.xaml.cpp OnPreviewPointerPressed: drop unused 'isPixelTraceTab' local.
- MainWindow.xaml.cpp OnPreviewPointerMoved: mark unused 'sender' parameter.

Author: Spruill-1

MainWindow.McpRoutes.cpp

@@ -188,10 +188,11 @@ static std::string NodeToJson(const ::ShaderLab::Graph::EffectNode& node)
         !node.analysisOutput.fields.empty())
     {
         json += ",\"analysisResults\":[";
-        bool first = true;
+        bool firstField = true;
         for (const auto& fv : node.analysisOutput.fields)
         {
-            if (!first) json += ",";
+            if (!firstField) json += ",";
+            firstField = false;
             json += "{\"name\":\"" + ToUtf8(fv.name) + "\"";
             if (!::ShaderLab::Graph::AnalysisFieldIsArray(fv.type))
             {
@@ -1036,7 +1037,6 @@ namespace winrt::ShaderLab::implementation
                 // Parse nodeId and optional /logs suffix from path.
                 // Expected: /node/{id}/logs or /node/{id}/logs?since={seq}
                 auto stripped = path.substr(6); // remove "/node/"
-                auto slashPos = stripped.find(L'/');
                 uint32_t nodeId = 0;
                 try { nodeId = static_cast<uint32_t>(std::stoi(stripped)); } catch (...) {
                     return { 400, R"({"error":"Invalid node ID"})" };

MainWindow.xaml.cpp

@@ -2273,8 +2273,6 @@ namespace winrt::ShaderLab::implementation
 
                     auto imgBounds = GetPreviewImageBounds();
                     float dpiScale = (std::max)(1.0f, PreviewPanel().CompositionScaleX());
-                    float imgDipX = (m_traceClickDipX - m_previewPanX) / m_previewZoom;
-                    float imgDipY = (m_traceClickDipY - m_previewPanY) / m_previewZoom;
                     float iW = imgBounds.right - imgBounds.left;
                     float iH = imgBounds.bottom - imgBounds.top;
                     if (iW <= 0 || iW > 100000.0f) { auto vp = PreviewViewportDips(); iW = vp.width; }
@@ -2375,9 +2373,8 @@ namespace winrt::ShaderLab::implementation
         winrt::Microsoft::UI::Xaml::Input::PointerRoutedEventArgs const& args)
     {
         auto point = args.GetCurrentPoint(PreviewPanel());
-        bool isPixelTraceTab = (BottomTabView().SelectedIndex() == 1);
 
-        // Left or middle button → start pan (click without drag triggers pixel trace on release).
+        // Left or middle button → start pan
         if (point.Properties().IsMiddleButtonPressed() || point.Properties().IsLeftButtonPressed())
         {
             m_isPreviewPanning = true;
@@ -2694,7 +2691,7 @@ namespace winrt::ShaderLab::implementation
     // -----------------------------------------------------------------------
 
     void MainWindow::OnPreviewPointerMoved(
-        winrt::Windows::Foundation::IInspectable const& sender,
+        winrt::Windows::Foundation::IInspectable const& /*sender*/,
         winrt::Microsoft::UI::Xaml::Input::PointerRoutedEventArgs const& args)
     {
         if (!m_renderEngine.IsInitialized()) return;