Add unit tests for Utils::toHex

test/mocks/Stream.h

@@ -0,0 +1,10 @@
+#pragma once
+
+// Mock Stream class for native testing
+// Provides minimal interface needed by Utils.h
+
+class Stream {
+public:
+    virtual void print(char c) {}
+    virtual void print(const char* str) {}
+};