Step 647: self-modification safety guard

editor/src/SelfModificationSafetyGuard.h

@@ -0,0 +1,28 @@
+#pragma once
+// Step 647: Self-modification safety guard
+
+#include <string>
+#include <vector>
+
+class SelfModificationSafetyGuard {
+public:
+    static bool isLiveBinaryPath(const std::string& filePath,
+                                 const std::vector<std::string>& liveRoots) {
+        for (const auto& root : liveRoots) {
+            if (!root.empty() && filePath.rfind(root, 0) == 0) return true;
+        }
+        return false;
+    }
+
+    static bool allowMutation(const std::string& filePath,
+                              const std::vector<std::string>& liveRoots,
+                              std::string* reason) {
+        if (!reason) return false;
+        reason->clear();
+        if (isLiveBinaryPath(filePath, liveRoots)) {
+            *reason = "Cannot mutate live binary - use a build/restart cycle.";
+            return false;
+        }
+        return true;
+    }
+};