feat: battle system, state manager enhancements, engine and demo updates

engine/types.ts

@@ -23,6 +23,8 @@ export interface SceneNode {
   skippable?: boolean
   streamingUrl?: Record<string, string>
   keyMoment?: boolean
+  battleHUD?: BattleHUDEntry[]
+  battleResult?: BattleResultDef
 }
 
 export interface Choice {
@@ -166,3 +168,31 @@ export interface PlayerTreeNode {
   isGateway?: boolean
   gatewayChapterId?: string
 }
+
+export interface BattleHUDStat {
+  variable: string
+  label: string
+  labelKey?: string
+  max?: number
+  style?: 'bar' | 'number'
+}
+
+export interface BattleHUDEntry {
+  label: string
+  labelKey?: string
+  portrait?: string
+  stats: BattleHUDStat[]
+}
+
+export interface BattleResultStat {
+  label: string
+  labelKey?: string
+  variable: string
+  max?: number
+}
+
+export interface BattleResultDef {
+  title: string
+  titleKey?: string
+  stats: BattleResultStat[]
+}