chore: sync from fn-registry agent

CMakeLists.txt

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+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
+    # fps_overlay vive en fn_framework
+)
+
+# --- E2E tests (opt-in via -DFN_BUILD_TESTS=ON) ---
+if(FN_BUILD_TESTS)
+    add_imgui_app(chart_demo_tests
+        main.cpp
+        tests/chart_demo_tests.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
+    )
+    # Excludes int main() from main.cpp so the test target provides its own.
+    target_compile_definitions(chart_demo_tests PRIVATE FN_TEST_BUILD)
+endif()

app.md

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+---
+name: chart_demo
+lang: cpp
+domain: viz
+description: "Demo ImGui de primitivos viz del registry: line_plot, scatter_plot, bar_chart, heatmap. Cada chart en su propia tab del TabBar. Usado como showcase y como build gate de las funciones viz/."
+tags: [imgui, demo, charts, viz, showcase]
+uses_functions:
+  - line_plot_cpp_viz
+  - scatter_plot_cpp_viz
+  - bar_chart_cpp_viz
+  - heatmap_cpp_viz
+  # logger, app_menubar viven en fn_framework — no se listan aqui
+uses_types: []
+framework: "imgui"
+entry_point: "main.cpp"
+dir_path: "cpp/apps/chart_demo"
+repo_url: ""
+---
+
+## Que hace
+
+App de una sola ventana con cuatro tabs (Line / Scatter / Bar / Heatmap) que
+renderiza datos sinteticos para mostrar el aspecto y la API de los primitivos
+viz del registry. Sirve como:
+
+- **Showcase visual** de las funciones viz existentes — al añadir una nueva
+  primitiva, anadir su tab aqui es la forma natural de probar el binding.
+- **Build gate**: si una de las funciones rompe API, esta app deja de
+  compilar y lo cazamos sin tener que tocar `registry_dashboard` o
+  `graph_explorer`.
+
+## Estructura
+
+`main.cpp` (~93 lineas):
+
+- `init_data()` — genera arrays sinteticos una vez (estado modulo).
+- `render()` — DockSpaceOverViewport + TabBar con 4 tabs, cada una invoca
+  un primitivo del registry.
+- `main()` → `fn::run_app(...)` con AppConfig estandar (titulo, tamaño,
+  about, log).
+
+## Build
+
+```bash
+# Linux
+cd cpp && cmake -B build/linux -S . && cmake --build build/linux --target chart_demo
+
+# Windows (cross-compile)
+cd cpp && cmake -B build/windows -S . -DCMAKE_TOOLCHAIN_FILE=toolchains/mingw-w64.cmake \
+  && cmake --build build/windows --target chart_demo
+```
+
+## Decisiones
+
+- `viewports = true` (default de `fn::run_app`): las ventanas se pueden
+  arrastrar fuera del main window.
+- `init_gl_loader = false`: solo usa ImGui/ImPlot, sin gl* directo.
+- Sin persistencia propia (no abre BD).
+- `log: file_path = "chart_demo.log"` con nivel Debug — el `init_data`
+  emite info+debug para verificar que el logger funciona.

main.cpp

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+#include "app_base.h"
+#include "imgui.h"
+#include "implot.h"
+
+#include "viz/line_plot.h"
+#include "viz/scatter_plot.h"
+#include "viz/bar_chart.h"
+#include "viz/heatmap.h"
+#include "core/app_menubar.h"
+#include "core/logger.h"
+
+#include <cmath>
+#include <vector>
+
+// Generate sample data
+static constexpr int N = 500;
+static float xs[N], ys_sin[N], ys_cos[N];
+static float scatter_x[200], scatter_y[200];
+static const char* bar_labels[] = {"Go", "Python", "Bash", "TypeScript", "C++"};
+static float bar_values[] = {201.0f, 202.0f, 38.0f, 80.0f, 5.0f};
+static float heat_data[10 * 10];
+
+static bool data_initialized = false;
+
+static void init_data() {
+    if (data_initialized) return;
+    fn_log::log_info("init_data: generando %d puntos sin/cos, 200 scatter, 10x10 heatmap", N);
+    for (int i = 0; i < N; i++) {
+        xs[i] = static_cast<float>(i) * 0.02f;
+        ys_sin[i] = sinf(xs[i]);
+        ys_cos[i] = cosf(xs[i]);
+    }
+    for (int i = 0; i < 200; i++) {
+        scatter_x[i] = static_cast<float>(rand()) / RAND_MAX * 10.0f;
+        scatter_y[i] = scatter_x[i] * 0.5f + (static_cast<float>(rand()) / RAND_MAX - 0.5f) * 3.0f;
+    }
+    for (int i = 0; i < 100; i++) {
+        int r = i / 10, c = i % 10;
+        heat_data[i] = sinf(r * 0.5f) * cosf(c * 0.5f);
+    }
+    data_initialized = true;
+    fn_log::log_debug("init_data: ok");
+}
+
+void render() {
+    init_data();
+
+    // MainMenuBar (solo Settings — chart_demo no tiene paneles toggleables)
+    fn_ui::app_menubar(nullptr, 0, nullptr);
+
+    // Full-window dockspace
+    ImGui::DockSpaceOverViewport(0, ImGui::GetMainViewport());
+
+    if (ImGui::Begin("fn_registry — Chart Demo")) {
+        if (ImGui::BeginTabBar("##charts")) {
+            if (ImGui::BeginTabItem("Line Plot")) {
+                ImGui::Text("sin(x) — %d points", N);
+                line_plot("Sine Wave", xs, ys_sin, N);
+                ImGui::EndTabItem();
+            }
+            if (ImGui::BeginTabItem("Scatter Plot")) {
+                ImGui::Text("y = 0.5x + noise — 200 points");
+                scatter_plot("Scatter Data", scatter_x, scatter_y, 200);
+                ImGui::EndTabItem();
+            }
+            if (ImGui::BeginTabItem("Bar Chart")) {
+                ImGui::Text("Functions per language in fn_registry");
+                bar_chart("Registry Languages", bar_labels, bar_values, 5);
+                ImGui::EndTabItem();
+            }
+            if (ImGui::BeginTabItem("Heatmap")) {
+                ImGui::Text("sin(r) * cos(c) — 10x10 matrix");
+                heatmap("Correlation Matrix", heat_data, 10, 10, -1.0f, 1.0f);
+                ImGui::EndTabItem();
+            }
+            ImGui::EndTabBar();
+        }
+    }
+    ImGui::End();
+}
+
+#ifndef FN_TEST_BUILD
+int main() {
+    return fn::run_app({
+        .title  = "fn_registry — Chart Demo",
+        .width  = 1400,
+        .height = 900,
+        .about  = {.name        = "chart demo",
+                   .version     = "0.2.0",
+                   .description = "Demo de primitivos viz: line, scatter, bar, heatmap. AppConfig estandar + multi-viewport."},
+        .log    = {.file_path = "chart_demo.log",
+                   .level     = static_cast<int>(fn_log::Level::Debug)}
+    }, render);
+}
+#endif

tests/chart_demo_tests.cpp

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+// E2E tests for chart_demo — Dear ImGui Test Engine.
+// Built only when -DFN_BUILD_TESTS=ON. The same main.cpp from chart_demo is
+// compiled here with FN_TEST_BUILD defined so its int main() is excluded and
+// only render() is reused.
+
+#include "app_base.h"
+#include "imgui.h"
+#include "imgui_te_engine.h"
+#include "imgui_te_context.h"
+
+void render();   // defined in chart_demo/main.cpp
+
+static void register_tests(ImGuiTestEngine* e) {
+    ImGuiTest* t = nullptr;
+
+    // Smoke test: the main window appears and is non-empty.
+    t = IM_REGISTER_TEST(e, "chart_demo", "smoke_window_visible");
+    t->TestFunc = [](ImGuiTestContext* ctx) {
+        ctx->SetRef("fn_registry \xe2\x80\x94 Chart Demo");   // em-dash
+        IM_CHECK(ctx->WindowInfo("").ID != 0);
+    };
+
+    // Cycle through all four tabs. Test engine fails the test if any tab item
+    // is not found or cannot be activated — that is our implicit assertion.
+    t = IM_REGISTER_TEST(e, "chart_demo", "tabs_cycle_all");
+    t->TestFunc = [](ImGuiTestContext* ctx) {
+        ctx->SetRef("fn_registry \xe2\x80\x94 Chart Demo");
+        ctx->ItemClick("##charts/Line Plot");
+        ctx->ItemClick("##charts/Scatter Plot");
+        ctx->ItemClick("##charts/Bar Chart");
+        ctx->ItemClick("##charts/Heatmap");
+    };
+}
+
+int main() {
+    fn::AppConfig cfg{};
+    cfg.title  = "chart_demo_tests";
+    cfg.width  = 1280;
+    cfg.height = 800;
+    return fn::run_app_test(cfg, render, register_tests);
+}