Findings of the resource atlas: engine and shell mods took these
resources from the content mod without depending on it.
- Main menu music (Serpent's Lament + the mainmenu playlist) -> base_menu.
- Battle win/defeat sounds -> turn_battle_base; UI sounds close_click and
skip -> interface; card selection effect -> card_battle.
- Journal notification texts (ui/journal/new, updated) -> quests_base;
settings screen texts (settings/*) -> base_menu.
- depends now declares characters_base, items_base and quests_base, whose
resources the content uses.