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/framework/app_base.cpp

@@ -0,0 +1,105 @@
+#include "app_base.h"
+
+#include "imgui.h"
+#include "imgui_impl_glfw.h"
+#include "imgui_impl_opengl3.h"
+#include "implot.h"
+
+#include <GLFW/glfw3.h>
+#include <cstdio>
+
+#ifdef TRACY_ENABLE
+#include "tracy/Tracy.hpp"
+#endif
+
+static void glfw_error_callback(int error, const char* description) {
+    fprintf(stderr, "GLFW Error %d: %s\n", error, description);
+}
+
+namespace fn {
+
+int run_app(AppConfig config, std::function<void()> render_fn) {
+    glfwSetErrorCallback(glfw_error_callback);
+    if (!glfwInit()) {
+        fprintf(stderr, "Failed to initialize GLFW\n");
+        return 1;
+    }
+
+    // OpenGL 3.3 core
+    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
+    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
+    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
+#ifdef __APPLE__
+    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
+#endif
+
+    GLFWwindow* window = glfwCreateWindow(config.width, config.height, config.title, nullptr, nullptr);
+    if (!window) {
+        fprintf(stderr, "Failed to create GLFW window\n");
+        glfwTerminate();
+        return 1;
+    }
+
+    glfwMakeContextCurrent(window);
+    glfwSwapInterval(config.vsync ? 1 : 0);
+
+    // Setup ImGui
+    IMGUI_CHECKVERSION();
+    ImGui::CreateContext();
+    ImPlot::CreateContext();
+
+    ImGuiIO& io = ImGui::GetIO();
+    io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;
+    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;
+
+    ImGui::StyleColorsDark();
+
+    ImGui_ImplGlfw_InitForOpenGL(window, true);
+    ImGui_ImplOpenGL3_Init("#version 330");
+
+    // Main loop
+    while (!glfwWindowShouldClose(window)) {
+        glfwPollEvents();
+
+        if (glfwGetWindowAttrib(window, GLFW_ICONIFIED)) {
+            glfwWaitEvents();
+            continue;
+        }
+
+        ImGui_ImplOpenGL3_NewFrame();
+        ImGui_ImplGlfw_NewFrame();
+        ImGui::NewFrame();
+
+        render_fn();
+
+        ImGui::Render();
+        int display_w, display_h;
+        glfwGetFramebufferSize(window, &display_w, &display_h);
+        glViewport(0, 0, display_w, display_h);
+        glClearColor(config.bg_r, config.bg_g, config.bg_b, 1.0f);
+        glClear(GL_COLOR_BUFFER_BIT);
+        ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
+
+        glfwSwapBuffers(window);
+
+#ifdef TRACY_ENABLE
+        FrameMark;
+#endif
+    }
+
+    // Cleanup
+    ImGui_ImplOpenGL3_Shutdown();
+    ImGui_ImplGlfw_Shutdown();
+    ImPlot::DestroyContext();
+    ImGui::DestroyContext();
+    glfwDestroyWindow(window);
+    glfwTerminate();
+
+    return 0;
+}
+
+int run_app(std::function<void()> render_fn) {
+    return run_app(AppConfig{}, render_fn);
+}
+
+} // namespace fn

cpp/framework/app_base.h

@@ -0,0 +1,25 @@
+#pragma once
+
+#include <functional>
+
+namespace fn {
+
+struct AppConfig {
+    const char* title = "fn_registry";
+    int width = 1280;
+    int height = 720;
+    bool vsync = true;
+    float bg_r = 0.1f;
+    float bg_g = 0.1f;
+    float bg_b = 0.1f;
+};
+
+// Run an ImGui application. The render_fn is called every frame
+// between ImGui::NewFrame() and ImGui::Render().
+// Returns 0 on clean exit, 1 on error.
+int run_app(AppConfig config, std::function<void()> render_fn);
+
+// Convenience: run with default config
+int run_app(std::function<void()> render_fn);
+
+} // namespace fn