Battle unit gauges extension point; battle action schemas

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

locale/schema_en.properties

@@ -0,0 +1,9 @@
+battle/schema/builtin/battle_init = Start a battle
+battle/schema/builtin/battle_init_desc = A battle from a novel scene: enemies, the return scene, a quest
+battle/schema/field/enemies = Enemies
+battle/schema/field/scene = Scene
+battle/schema/field/quest = Quest
+battle/schema/field/tag = Tag
+battle/schema/builtin/set_core = Battle core
+battle/schema/builtin/set_core_desc = Which rules the next battle follows
+battle/schema/field/core = Core