feat: add C++ ImGui functions for core UI and visualization

Funciones C++/ImGui para dashboards (grid, panel, docking, sidebar, tabs),
visualizaciones (candlestick, gauge, histogram, pie, sparkline, heatmap,
scatter, line, bar, surface3d, kpi, table), grafos (force layout, renderer,
viewport, spatial hash, types) y utilidades (time series buffer, tracy zones,
memory/fps overlay, plot theme).

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

cpp/functions/viz/sparkline.cpp

@@ -0,0 +1,76 @@
+#include "viz/sparkline.h"
+#include "imgui.h"
+
+void sparkline(const char* id, const float* values, int count, ImVec4 color,
+               float width, float height) {
+    if (count <= 0) return;
+
+    ImGui::PushID(id);
+
+    ImVec2 pos = ImGui::GetCursorScreenPos();
+    ImDrawList* draw_list = ImGui::GetWindowDrawList();
+
+    // Reserve inline space
+    ImGui::Dummy(ImVec2(width, height));
+
+    // Find min/max for Y auto-scale
+    float min_val = values[0];
+    float max_val = values[0];
+    for (int i = 1; i < count; i++) {
+        if (values[i] < min_val) min_val = values[i];
+        if (values[i] > max_val) max_val = values[i];
+    }
+    float range = max_val - min_val;
+    if (range < 1e-6f) range = 1.0f; // avoid division by zero for flat lines
+
+    // Fill area under curve (low alpha)
+    if (count >= 2) {
+        ImU32 fill_color = IM_COL32(
+            (int)(color.x * 255),
+            (int)(color.y * 255),
+            (int)(color.z * 255),
+            40);
+
+        // Build fill polygon: baseline bottom-left -> points -> baseline bottom-right
+        // We use AddConvexPolyFilled workaround: draw as a series of triangles from baseline
+        float x0 = pos.x;
+        float y_base = pos.y + height;
+
+        for (int i = 0; i + 1 < count; i++) {
+            float xa = x0 + ((float)i       / (count - 1)) * width;
+            float xb = x0 + ((float)(i + 1) / (count - 1)) * width;
+            float ya = pos.y + height - ((values[i]     - min_val) / range) * height;
+            float yb = pos.y + height - ((values[i + 1] - min_val) / range) * height;
+
+            draw_list->AddQuadFilled(
+                ImVec2(xa, y_base),
+                ImVec2(xa, ya),
+                ImVec2(xb, yb),
+                ImVec2(xb, y_base),
+                fill_color);
+        }
+    }
+
+    // Draw polyline
+    ImU32 line_color = IM_COL32(
+        (int)(color.x * 255),
+        (int)(color.y * 255),
+        (int)(color.z * 255),
+        (int)(color.w * 255));
+
+    for (int i = 0; i + 1 < count; i++) {
+        float xa = pos.x + ((float)i       / (count - 1)) * width;
+        float xb = pos.x + ((float)(i + 1) / (count - 1)) * width;
+        float ya = pos.y + height - ((values[i]     - min_val) / range) * height;
+        float yb = pos.y + height - ((values[i + 1] - min_val) / range) * height;
+        draw_list->AddLine(ImVec2(xa, ya), ImVec2(xb, yb), line_color, 1.5f);
+    }
+
+    ImGui::PopID();
+}
+
+void sparkline(const char* id, const float* values, int count,
+               float width, float height) {
+    // Default color: soft green
+    sparkline(id, values, count, ImVec4(0.35f, 0.85f, 0.45f, 1.0f), width, height);
+}