feat: add C++ support with ImGui/ImPlot framework and vendor submodules

Añade soporte C++ al registry: vendor submodules (glfw, imgui, implot, tracy),
sistema de build con CMake y toolchains cross-platform, runner C++ en fn CLI,
parser de tests Google Test, y funciones bash para build Linux/Windows.

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

cpp/functions/viz/heatmap.h

@@ -0,0 +1,9 @@
+#pragma once
+
+// Renders a heatmap using ImPlot.
+// Data is row-major: values[row * cols + col].
+// Call within an ImGui frame.
+void heatmap(const char* title, const float* values, int rows, int cols,
+             float scale_min = 0.0f, float scale_max = 0.0f);
+void heatmap(const char* title, const double* values, int rows, int cols,
+             double scale_min = 0.0, double scale_max = 0.0);