feat(engine): loop idle runner with enabledLoopActionIds

src/engine/game.ts

@@ -26,6 +26,8 @@ export interface GameState {
   currentStoryNodeId: string;
   /** Story node ids the player has already seen. */
   seenStoryNodeIds: string[];
+  /** loop-kind action id -> whether the player has enabled it for idle running. */
+  enabledLoopActionIds: Record<string, boolean>;
 }
 
 export function createGameState(content: Content): GameState {
@@ -41,6 +43,7 @@ export function createGameState(content: Content): GameState {
     storyFlags: {},
     currentStoryNodeId: '',
     seenStoryNodeIds: [],
+    enabledLoopActionIds: {},
   };
 }
 
@@ -197,6 +200,26 @@ export function executeStoryAction(
   applyChoice(state, content, action.storyChoiceId);
 }
 
+/**
+ * Start the highest-priority enabled, available loop action when the game is idle.
+ * Invoked by the runtime AFTER each live tick — never from `tickGame`, so loop
+ * actions do not run during offline catch-up (which replays `tickGame` directly).
+ */
+export function maybeStartLoopAction(state: GameState, content: Content): void {
+  if (state.activeActionId !== null || state.actionQueue.length > 0) return;
+
+  const candidates = content.actions
+    .filter((a) => a.kind === 'loop' && state.enabledLoopActionIds[a.id])
+    .sort((a, b) => (a.loopPriority ?? 0) - (b.loopPriority ?? 0));
+
+  for (const action of candidates) {
+    if (isActionAvailable(state, content, action.id)) {
+      beginAction(state, content, action.id);
+      return;
+    }
+  }
+}
+
 /**
  * Advance the active action by `tickMs`. On completion, grants yields and
  * advances the queue — actions do not auto-repeat when the queue is empty.