feat(udpscope): build scaffold and min/max envelope decimation

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Client/udpscope/Types.h

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+/**
+ * @file Types.h
+ * @brief Plain data shared across UDPScope modules. No logic, no dependencies.
+ */
+#pragma once
+
+#include <cstddef>
+#include <cstdint>
+#include <string>
+#include <vector>
+
+namespace udpscope {
+
+/** A time series as two parallel arrays, which is what ImPlot wants. */
+struct Series {
+    std::vector<double> t;
+    std::vector<double> v;
+
+    void clear() { t.clear(); v.clear(); }
+    size_t size() const { return t.size(); }
+    bool empty() const { return t.empty(); }
+};
+
+/** RGBA in 0..1. Framework-free so PaneTree needs no ImGui. */
+struct Color {
+    float r = 1.f, g = 1.f, b = 1.f, a = 1.f;
+};
+
+/** Screen rectangle in pixels. */
+struct Rect {
+    double x = 0.0, y = 0.0, w = 0.0, h = 0.0;
+
+    bool contains(double px, double py) const {
+        return px >= x && px < (x + w) && py >= y && py < (y + h);
+    }
+};
+
+} /* namespace udpscope */