修复行为树关键bug

- 修复BehaviorTree.ts中lastOpenNodes的空指针风险
- 修复Ticker.ts中closeNode栈操作不对称问题
- 修复Agent.ts中subject参数传递错误

🤖 Generated with [Claude Code](https://claude.ai/code)

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

src/behaviortree/BehaviorTree.ts

@@ -32,7 +32,7 @@ export class BehaviorTree {
         ticker.openNodes.length = 0;
         this._root._execute(ticker);
         // 上次打开的节点
-        let lastOpenNodes = blackboard.get("openNodes", this._id) as BaseNode[];
+        let lastOpenNodes = (blackboard.get("openNodes", this._id) || []) as BaseNode[];
         // 当前打开的节点
         let currOpenNodes = ticker.openNodes;
         let start = 0;