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/core/fps_overlay.cpp

@@ -0,0 +1,33 @@
+#include "core/fps_overlay.h"
+#include "imgui.h"
+
+#ifdef TRACY_ENABLE
+#include "tracy/Tracy.hpp"
+#endif
+
+void fps_overlay() {
+#ifdef TRACY_ENABLE
+    ZoneScoped;
+#endif
+
+    ImGuiIO& io = ImGui::GetIO();
+    ImGuiWindowFlags flags = ImGuiWindowFlags_NoDecoration
+                           | ImGuiWindowFlags_AlwaysAutoResize
+                           | ImGuiWindowFlags_NoSavedSettings
+                           | ImGuiWindowFlags_NoFocusOnAppearing
+                           | ImGuiWindowFlags_NoNav
+                           | ImGuiWindowFlags_NoMove;
+
+    const float pad = 10.0f;
+    const ImGuiViewport* viewport = ImGui::GetMainViewport();
+    ImVec2 pos(viewport->WorkPos.x + viewport->WorkSize.x - pad,
+               viewport->WorkPos.y + pad);
+    ImGui::SetNextWindowPos(pos, ImGuiCond_Always, ImVec2(1.0f, 0.0f));
+    ImGui::SetNextWindowBgAlpha(0.65f);
+
+    if (ImGui::Begin("##fps_overlay", nullptr, flags)) {
+        ImGui::Text("%.1f FPS", io.Framerate);
+        ImGui::Text("%.3f ms", 1000.0f / io.Framerate);
+    }
+    ImGui::End();
+}

cpp/functions/core/fps_overlay.h

@@ -0,0 +1,5 @@
+#pragma once
+
+// Renders an FPS counter overlay in the top-right corner.
+// Call within an ImGui frame.
+void fps_overlay();

cpp/functions/core/fps_overlay.md

@@ -0,0 +1,30 @@
+---
+name: fps_overlay
+kind: component
+lang: cpp
+domain: core
+version: "1.0.0"
+purity: pure
+signature: "void fps_overlay()"
+description: "Renderiza un overlay de FPS y frametime en la esquina superior derecha, con soporte opcional de Tracy"
+tags: [imgui, fps, overlay, profiling, debug]
+uses_functions: []
+uses_types: []
+returns: []
+returns_optional: false
+error_type: ""
+imports: [imgui]
+tested: false
+tests: []
+test_file_path: ""
+file_path: "cpp/functions/core/fps_overlay.cpp"
+framework: imgui
+params: []
+output: "Renderiza el overlay de FPS en el frame ImGui actual"
+---
+
+# fps_overlay
+
+Muestra FPS y frametime (ms) en una ventana semi-transparente en la esquina superior derecha.
+
+Si se compila con `TRACY_ENABLE`, incluye un `ZoneScoped` para profiling con Tracy.