A .nacapack is what one project offers another, with everything it needs. Installed, it is a folder (packs/signpost/), and a game loads it the way it loads a texture or a model: useLoadPack hands it back at once and fills it in when it lands, and createPack places a copy of what it offers.
Each copy has its own place and its own settings (props), and the pack's input action is added to the game for you: press E and both signposts jump. Its scripts are code, so they come in with one import of signpost.pack.ts.