feat(engine): 添加MCP连接管理和工具集成功能

- 集成MCP连接管理器，支持MCP服务器连接
- 添加多种内置工具：ClarifyTool、CronTool、DelegateTool、ExecuteCodeTool、
  PatchFileTool、ProcessTool、SendMessageTool、SpawnTool、TerminalTool、
  TodoTool、WebFetchTool、WebSearchTool、WriteFileTool等
- 实现工具注册和装配功能
- 添加技能选择上下文参数
- 支持思考模式控制参数thinking_enabled

feat(coordinator): 重构任务执行计划器参数命名

- 将learning_candidate_enabled重命名为allow_candidate_generation
- 更新TeamGraphScheduler中的参数传递
- 修改LocalAgentRunner中的相关参数处理
- 更新README文档中的相应描述

refactor(context): 标准化工具调用参数格式

- 添加_json导入用于参数序列化
- 实现_provider_tool_calls方法标准化OpenAI兼容的工具调用载荷
- 修复工具调用中参数非字符串类型的序列化问题

refactor(session): 优化消息历史记录过滤逻辑

- 修改get_messages_as_conversation为基于运行状态过滤消息
- 排除未完成、失败或错误结束的运行记录
- 改进对话历史的可见性控制机制

fix(store): 修复FTS索引重建逻辑

- 添加异常处理防止FTS索引创建失败
- 实现_rebuild_fts_index方法重新构建全文搜索索引
- 优化索引触发器和表的维护流程

app-instance/backend/beaver/tasks/store.py

@@ -40,7 +40,7 @@ class TaskStore:
         tasks = [
             task
             for task in self.list_tasks()
-            if task.session_id == session_id and task.status in {"awaiting_feedback", "needs_revision", "open", "running"}
+            if task.session_id == session_id and task.is_open
         ]
         if not tasks:
             return None
@@ -52,6 +52,25 @@ class TaskStore:
             payload[task.task_id] = task.to_dict()
             self._write_tasks_unlocked(payload)
 
+    def delete_task(self, task_id: str) -> bool:
+        with self._lock:
+            payload = self._read_tasks_unlocked()
+            if task_id not in payload:
+                return False
+            payload.pop(task_id, None)
+            self._write_tasks_unlocked(payload)
+            if self.events_path.exists():
+                kept = []
+                for line in self.events_path.read_text(encoding="utf-8").splitlines():
+                    cleaned = line.strip()
+                    if not cleaned:
+                        continue
+                    event_payload = json.loads(cleaned)
+                    if not isinstance(event_payload, dict) or str(event_payload.get("task_id")) != task_id:
+                        kept.append(cleaned)
+                self.events_path.write_text(("\n".join(kept) + "\n") if kept else "", encoding="utf-8")
+            return True
+
     def append_event(self, event: TaskEvent) -> None:
         self.events_path.parent.mkdir(parents=True, exist_ok=True)
         with self._lock: