feat: add C++ ImGui functions for core UI and visualization

Funciones C++/ImGui para dashboards (grid, panel, docking, sidebar, tabs),
visualizaciones (candlestick, gauge, histogram, pie, sparkline, heatmap,
scatter, line, bar, surface3d, kpi, table), grafos (force layout, renderer,
viewport, spatial hash, types) y utilidades (time series buffer, tracy zones,
memory/fps overlay, plot theme).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cpp/functions/viz/surface_plot_3d.cpp

@@ -0,0 +1,12 @@
+#include "viz/surface_plot_3d.h"
+#include "imgui.h"
+
+void surface_plot_3d(const char* title, const float* values, int rows, int cols,
+                     float z_min, float z_max) {
+    ImGui::BeginGroup();
+    ImGui::TextDisabled("[STUB] %s", title);
+    ImGui::TextWrapped("surface_plot_3d requires ImPlot3D. "
+                       "Add it to cpp/vendor/implot3d/ and rebuild.");
+    ImGui::Text("Data: %dx%d, range [%.2f, %.2f]", rows, cols, z_min, z_max);
+    ImGui::EndGroup();
+}