refactor: global state for scenes

packages/sts-like-viewer/src/state/gameState.ts

@@ -0,0 +1,29 @@
+import { MutableSignal, mutableSignal } from 'boardgame-core';
+import { createRunState, type RunState } from 'boardgame-core/samples/slay-the-spire-like';
+
+/**
+ * 全局游戏运行状态 Signal
+ * 
+ * 在 App.tsx 中创建为单例，所有场景共享。
+ * 遭遇场景通过读取此 signal 的当前遭遇状态来构建 UI。
+ */
+export function createGameState(seed?: number): MutableSignal<RunState> {
+  return mutableSignal<RunState>(createRunState(seed));
+}
+
+/** 获取当前遭遇数据（computed getter） */
+export function currentEncounter(
+  gameState: MutableSignal<RunState>
+): { nodeId: string; encounter: { name: string; description: string; type: string } } | null {
+  const state = gameState.value;
+  const node = state.map.nodes.get(state.currentNodeId);
+  if (!node || !node.encounter) return null;
+  return {
+    nodeId: node.id,
+    encounter: {
+      type: node.type,
+      name: node.encounter.name,
+      description: node.encounter.description,
+    },
+  };
+}