feat(core): add world snapshot serialization helpers

core/include/vf/Serialize.h

@@ -0,0 +1,18 @@
+#pragma once
+
+#include <cstdint>
+#include <vector>
+#include "World.h"
+
+namespace vf {
+
+// Binary world format "VXF1": magic, version, chunk count, then per chunk the
+// coordinate and a run-length-encoded block stream. Compact for the large
+// runs of air and stone that voxel terrain produces.
+std::vector<uint8_t> serializeWorld(const World& world);
+
+// Rebuilds `out` from a serialized buffer. Returns false on a bad magic,
+// version, or truncated stream.
+bool deserializeWorld(const uint8_t* data, std::size_t size, World& out);
+
+} // namespace vf