s&box SaveSystem: [Sync]-only properties need separate snapshot/restore — they are not captured by scene diff

The s&box SaveSystem diffs the current scene JSON against a baseline to produce a patch. However, [Sync] properties that are NOT also marked [Property] are not serialized into the scene JSON — they exist only in network state. After loading a save, these values revert to defaults, causing desync between what was saved and what is restored (e.g. health, ammo, custom networked state).