-spec register_game_modes() -> ok.

Register the Lua bridge modules as the providers for the three Lua game-mode kinds asobi_game_modes knows about.

Called from asobi_app:start/2 before the supervision tree comes up, and by any test that resolves a {lua, _} mode without booting the application. The mapping lives here, next to the bridges, so asobi_game_modes keeps knowing nothing about the scripting runtime.