Restructure C++ core into cpp module and package bindings.

Move the pricing engine sources out of src/ into cpp/, add the closed-form engine and pybind wiring, and align tests/build targets with the new project layout.

Made-with: Cursor

cpp/Statistics.cpp

@@ -0,0 +1,53 @@
+/**
+ * @file Statistics.cpp
+ * @brief Streaming moment and extrema updates.
+ */
+
+#include "Statistics.hpp"
+
+void Statistics::dump(double value) {
+    for (std::size_t i = 0; i < 3; ++i) {
+        moments_[i] += std::pow(value, i+1);
+    }
+    ++n;
+    max_ = std::max(max_, value);
+    min_ = std::min(min_, value);
+}
+
+void Statistics::clear() {
+    n = 0;
+    moments_ = {0.,0.,0.};
+}
+
+double Statistics::mean() {
+    return moments_[0]/n;
+}
+
+double Statistics::variance() {
+    return moments_[1]/n - std::pow(mean(), 2);
+}
+
+double Statistics::standardDeviation() {
+    return std::sqrt(variance());
+}
+
+double Statistics::skewness() {
+    return moments_[2]/std::pow(n, 3);
+}
+
+
+double Statistics::max() {
+    return max_;
+}
+
+double Statistics::min() {
+    return min_;
+}
+
+double Statistics::sum() {
+    return moments_[0];
+}
+
+double Statistics::count() {
+    return n;
+}