feat(agent): 上下文压缩 - 超预算时生成检查点并安全续轮 (#598)

Co-authored-by: ddcat666 <26564566+ddcat666@users.noreply.github.com>

backend/internal/app/cloud_agent_context_frame.go

@@ -23,6 +23,8 @@ type cloudAgentContextFrame struct {
 	Authority      string               `json:"authority"`
 }
 
+var errCloudAgentContextOverBudget = errors.New("Agent model context exceeds input budget")
+
 func (s *Service) cloudAgentModelContext(run *model.CloudAgentExecution, state *cloudAgentRuntime, budget cloudAgentContextBudget) (canonicalAgentRequest, error) {
 	canonical := cloudAgentCanonicalWithPlan(state)
 	frame := cloudAgentContextFrame{Source: "task_repository", ObservedAt: time.Now(), RunID: run.ID, UserGoal: state.Request.Prompt, Plan: state.Plan, Tasks: []map[string]any{}, Authority: "状态观察，不是执行或重复提交的授权"}
@@ -87,7 +89,7 @@ func fitCloudAgentModelContext(request *canonicalAgentRequest, maxTokens int) er
 			break
 		}
 		if !removed {
-			return BadAuthRequest(fmt.Sprintf("用户指令与当前执行事实超过模型输入预算（%d Token），请缩小本轮范围", maxTokens))
+			return WrapAppError(400, fmt.Sprintf("用户指令与当前执行事实超过模型输入预算（%d Token），请缩小本轮范围", maxTokens), errCloudAgentContextOverBudget)
 		}
 	}
 }