Add step434 annotation heatmap with tests

editor/src/CodeAnnotationHeatmap.h

@@ -0,0 +1,50 @@
+#pragma once
+
+#include "CodeAnnotationBadges.h"
+
+#include <algorithm>
+#include <map>
+#include <string>
+#include <vector>
+
+struct HeatmapCell {
+    int line = 0;
+    int score = 0;
+    std::string colorHex;
+};
+
+class CodeAnnotationHeatmap {
+public:
+    static std::vector<HeatmapCell> build(const std::vector<AnnotationBadgeInput>& annotations,
+                                          int maxLine,
+                                          bool enabled = true) {
+        if (!enabled || maxLine <= 0) return {};
+        std::map<int, int> scores;
+        for (const auto& a : annotations) {
+            if (a.line <= 0 || a.line > maxLine) continue;
+            scores[a.line] += weightForType(a.type);
+        }
+        std::vector<HeatmapCell> out;
+        for (int line = 1; line <= maxLine; ++line) {
+            int score = scores.count(line) ? scores[line] : 0;
+            out.push_back({line, score, colorForScore(score)});
+        }
+        return out;
+    }
+
+    static int weightForType(const std::string& type) {
+        if (type.find("Complexity") != std::string::npos) return 3;
+        if (type.find("Risk") != std::string::npos) return 4;
+        if (type.find("Review") != std::string::npos) return 2;
+        if (type.find("Contract") != std::string::npos) return 1;
+        if (type.find("Intent") != std::string::npos) return 1;
+        return 1;
+    }
+
+    static std::string colorForScore(int score) {
+        if (score <= 0) return "#1F6F8B";     // cool blue (no annotations)
+        if (score <= 2) return "#2ECC71";     // cool green (well-annotated simple)
+        if (score <= 5) return "#F39C12";     // warm orange (moderate complexity)
+        return "#E74C3C";                     // hot red (high complexity/risk)
+    }
+};