Started migrating game state to a proper data layer. Added BuildingState types that serialize building state into plain objects for the React layer, with a buildingsAtom that bridges the game engine and UI. Introduced useGameOperations as a React hook to access the game operations facade.

Updated all HUD components to consume state through the new atoms instead of reaching into game objects directly. Buildings now expose serialization methods to produce their state snapshots. This is the first step toward fully decoupling the rendering engine from the React UI.