Add renderer purpose display toggles (Guide, Proxy, Render)

Exposes UsdGeomImageable purpose visibility as three per-viewport toggles
in the gear popup (Purpose: Guide / Proxy / Render), wired to
showGuides/showProxy/showRender on UsdImagingGLRenderParams. Defaults match
the USD render params defaults (Proxy on, Guide and Render off). Settings
persist per-viewport to viewport_settings.ini.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/ui/ViewportPanel.cpp

@@ -659,6 +659,9 @@ void ViewportPanel::SaveSettings(const std::string& path) const
         f << "ShowGrid="         << (s.showGrid        ? 1 : 0) << "\n";
         f << "ShowCameraGuide="  << (s.showCameraGuide ? 1 : 0) << "\n";
         f << "Aov="              << s.aov              << "\n";
+        f << "ShowGuides="       << (s.showGuides      ? 1 : 0) << "\n";
+        f << "ShowProxy="        << (s.showProxy       ? 1 : 0) << "\n";
+        f << "ShowRender="       << (s.showRender      ? 1 : 0) << "\n";
         f << "AAEnabled="        << (s.aaEnabled        ? 1 : 0) << "\n";
         f << "BgColorR="         << s.bgColorR          << "\n";
         f << "BgColorG="         << s.bgColorG          << "\n";
@@ -727,6 +730,9 @@ void ViewportPanel::LoadSettings(const std::string& path)
             else if (key == "ShowGrid")         ts.showGrid         = (val == "1");
             else if (key == "ShowCameraGuide")  ts.showCameraGuide  = (val == "1");
             else if (key == "Aov")              ts.aov              = val;
+            else if (key == "ShowGuides")       ts.showGuides       = (val == "1");
+            else if (key == "ShowProxy")        ts.showProxy        = (val == "1");
+            else if (key == "ShowRender")       ts.showRender       = (val == "1");
             else if (key == "AAEnabled")        ts.aaEnabled        = (val == "1");
             else if (key == "BgColorR")         ts.bgColorR         = toFloat(val, ts.bgColorR);
             else if (key == "BgColorG")         ts.bgColorG         = toFloat(val, ts.bgColorG);

src/ui/ViewportTile.cpp

@@ -96,6 +96,9 @@ ViewportTileSettings ViewportTile::GetSettings() const
     s.showGrid         = m_renderer.ShowGrid();
     s.showCameraGuide  = m_renderer.ShowCameraGuide();
     s.aov              = m_renderer.GetCurrentAov().GetString();
+    s.showGuides       = m_renderer.ShowGuides();
+    s.showProxy        = m_renderer.ShowProxy();
+    s.showRender       = m_renderer.ShowRender();
     s.aaEnabled        = m_renderer.GetAAEnabled();
     const pxr::GfVec3f& bg = m_renderer.GetBackgroundColor();
     s.bgColorR = bg[0]; s.bgColorG = bg[1]; s.bgColorB = bg[2];
@@ -114,6 +117,9 @@ void ViewportTile::ApplySettings(const ViewportTileSettings& s)
     m_renderer.SetShowCameraGuide(s.showCameraGuide);
     if (!s.aov.empty())
         m_renderer.SetCurrentAov(pxr::TfToken(s.aov));
+    m_renderer.SetShowGuides(s.showGuides);
+    m_renderer.SetShowProxy(s.showProxy);
+    m_renderer.SetShowRender(s.showRender);
     m_renderer.SetAAEnabled(s.aaEnabled);
     m_renderer.SetBackgroundColor(pxr::GfVec3f(s.bgColorR, s.bgColorG, s.bgColorB));
     m_renderer.SetBBoxMode(static_cast<BBoxMode>(s.bboxMode));
@@ -1052,6 +1058,17 @@ void ViewportTile::RenderCompactToolbar(int tileIndex)
                 if (ImGui::MenuItem("Camera Guide", nullptr, guide))
                     m_renderer.SetShowCameraGuide(!guide);
 
+                ImGui::Separator();
+                bool purGuide = m_renderer.ShowGuides();
+                if (ImGui::MenuItem("Purpose: Guide",  nullptr, purGuide))
+                    m_renderer.SetShowGuides(!purGuide);
+                bool purProxy = m_renderer.ShowProxy();
+                if (ImGui::MenuItem("Purpose: Proxy",  nullptr, purProxy))
+                    m_renderer.SetShowProxy(!purProxy);
+                bool purRender = m_renderer.ShowRender();
+                if (ImGui::MenuItem("Purpose: Render", nullptr, purRender))
+                    m_renderer.SetShowRender(!purRender);
+
                 bool aaItem = m_renderer.GetAAEnabled();
                 if (ImGui::MenuItem("Anti-Aliasing", nullptr, aaItem))
                     m_renderer.SetAAEnabled(!aaItem);

src/ui/ViewportTile.h

@@ -32,6 +32,9 @@ struct ViewportTileSettings {
     bool        ambientLightOnly = true;
     bool        domeLightEnabled = false;
     int         shadingMode      = 0;
+    bool        showGuides       = false;
+    bool        showProxy        = true;
+    bool        showRender       = false;
 };
 
 /// Named orthographic view directions.