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/apps/chart_demo/CMakeLists.txt

@@ -0,0 +1,8 @@
+add_imgui_app(chart_demo
+    main.cpp
+    ${CMAKE_SOURCE_DIR}/functions/viz/line_plot.cpp
+    ${CMAKE_SOURCE_DIR}/functions/viz/scatter_plot.cpp
+    ${CMAKE_SOURCE_DIR}/functions/viz/bar_chart.cpp
+    ${CMAKE_SOURCE_DIR}/functions/viz/heatmap.cpp
+    ${CMAKE_SOURCE_DIR}/functions/core/fps_overlay.cpp
+)