feat(engine): 添加运行时上下文支持并重构工具迭代限制

添加 RuntimeContext 类用于捕获模型运行时的日期时间信息，
包括UTC时间、本地时间和时区信息，并在系统提示中显示这些信息。

同时增加最大上下文消息数和工具迭代次数的配置选项，
将验证服务从引擎加载器中移除，并更新相关的数据结构和接口。

BREAKING CHANGE: 移除了验证服务，相关字段被替换为证据状态和接受状态。

- 添加 RuntimeContext 类和相关渲染方法
- 增加 max_context_messages 和 max_tool_iterations 配置
- 移除 ValidationService 相关代码
- 更新消息记录中的验证状态字段
- 添加原始工具调用检测和回退处理

app-instance/backend/beaver/services/process_service.py

@@ -235,26 +235,45 @@ class SessionProcessProjector:
                         metadata=dict(payload),
                     )
 
-            elif record.event_type == "task_validation_snapshotted":
-                validation = payload.get("validation_result") if isinstance(payload.get("validation_result"), dict) else {}
-                accepted = bool(validation.get("accepted"))
-                root["status"] = "done" if accepted or attempt_index == 2 else "waiting"
-                root["finished_at"] = created_at if root["status"] == "done" else None
+            elif record.event_type == "task_evidence_recorded":
+                root["status"] = "waiting"
+                root["finished_at"] = None
                 add_event(
-                    event_id=_event_id(record, "validation"),
+                    event_id=_event_id(record, "evidence"),
                     run_id=record.run_id or root_run_id,
                     parent_run_id=root_run_id if record.run_id else None,
                     kind="run_status",
                     actor_type="system",
-                    actor_id="validator",
-                    actor_name="Validator",
-                    text=(
-                        f"Validation {'passed' if accepted else 'failed'} "
-                        f"(score={validation.get('score')})."
-                        + (" Retry scheduled." if payload.get("retry_scheduled") else "")
-                    ),
+                    actor_id="evidence-recorder",
+                    actor_name="Evidence",
+                    text="Task evidence was recorded; waiting for user acceptance.",
                     created_at=created_at,
-                    status="done" if accepted else "error",
+                    status="done",
+                    metadata=dict(payload),
+                )
+
+            elif record.event_type == "task_acceptance_recorded":
+                acceptance_type = str(payload.get("acceptance_type") or payload.get("feedback_type") or "")
+                if acceptance_type == "accept":
+                    root["status"] = "done"
+                    root["finished_at"] = created_at
+                elif acceptance_type == "abandon":
+                    root["status"] = "cancelled"
+                    root["finished_at"] = created_at
+                else:
+                    root["status"] = "waiting"
+                    root["finished_at"] = None
+                add_event(
+                    event_id=_event_id(record, "acceptance"),
+                    run_id=record.run_id or root_run_id,
+                    parent_run_id=root_run_id if record.run_id else None,
+                    kind="run_status",
+                    actor_type="user",
+                    actor_id="user-acceptance",
+                    actor_name="User Acceptance",
+                    text=f"User acceptance recorded: {acceptance_type or 'unknown'}.",
+                    created_at=created_at,
+                    status="done",
                     metadata=dict(payload),
                 )