fix(agent): Agent 运行 - 重复读取改为软收敛并保留可纠正的媒体失败原因

重复只读和同版本识图不再把运行标成失败，下一步暂时收起只读工具。媒体能力错误改为可纠正，准入失败保留安全原因。

backend/internal/app/cloud_agent_vision_delivery_test.go

@@ -380,10 +380,72 @@ func TestCloudAgentVisionBlocksSameResourceInSameCanvasRevision(t *testing.T) {
 	state.ImageInspectionReads = map[string]int{inspection.CacheKey: 1}
 
 	refreshCall := cloudAgentStoryboardCall(t, "canvas_inspect_image", "inspect-refresh", map[string]any{"nodeId": "cat", "refresh": true})
-	_, err = s.prepareCloudAgentImageInspection("user", "agent-canvas", &state, refreshCall)
-	var loopErr *cloudAgentReadLoopError
-	if !errors.As(err, &loopErr) {
-		t.Fatalf("refresh should not re-read the same resource in the same revision: %v", err)
+	second, err := s.prepareCloudAgentImageInspection("user", "agent-canvas", &state, refreshCall)
+	if err != nil {
+		t.Fatalf("repeated visual read should converge to a receipt, got: %v", err)
+	}
+	receipt := second.(cloudAgentImageInspection)
+	if receipt.ImageURL != "" || receipt.Receipt["repeat"] != true || receipt.CacheKey != inspection.CacheKey {
+		t.Fatalf("repeated visual read did not return a stable text receipt: %+v", receipt)
+	}
+}
+
+func TestCloudAgentVisionRepeatReadSoftNudgesRuntime(t *testing.T) {
+	s, _, _ := cloudAgentVisionFixture(t)
+	req := agentTestRequest()
+	req.VisionEnabled = true
+	root, err := s.CreateCloudAgentRun("user", req, "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	run, err := s.repo.CloudAgent("user", root.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	state, err := cloudAgentDecode(run)
+	if err != nil {
+		t.Fatal(err)
+	}
+	state.Request.VisionEnabled = true
+	firstCall := cloudAgentStoryboardCall(t, "canvas_inspect_image", "inspect-first", map[string]any{"nodeId": "cat"})
+	first, err := s.prepareCloudAgentImageInspection("user", "agent-canvas", &state, firstCall)
+	if err != nil {
+		t.Fatal(err)
+	}
+	cacheKey := first.(cloudAgentImageInspection).CacheKey
+	state.ImageInspectionReads = map[string]int{cacheKey: 1}
+	state.Calls = []cloudAgentCall{cloudAgentStoryboardCall(t, "canvas_inspect_image", "inspect-repeat", map[string]any{"nodeId": "cat", "refresh": true})}
+	state.CallIndex = 0
+	if err := s.repo.MutateCloudAgent("user", run.ID, run.Revision, func(current *model.CloudAgentExecution, _ *repository.Repository) error {
+		return cloudAgentSave(current, &state)
+	}); err != nil {
+		t.Fatal(err)
+	}
+	run, err = s.repo.CloudAgent("user", root.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	state, err = cloudAgentDecode(run)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := s.advanceCloudAgentTool(run, &state); err != nil {
+		t.Fatal(err)
+	}
+	output, err := s.CloudAgentRun("user", root.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if output.Status != "running" {
+		t.Fatalf("repeat visual read terminated the run: %+v", output)
+	}
+	hasGuard, hasFailure := false, false
+	for _, event := range output.Events {
+		hasGuard = hasGuard || event.Type == "read_loop_guard"
+		hasFailure = hasFailure || event.Type == "run_failed"
+	}
+	if !hasGuard || hasFailure {
+		t.Fatalf("repeat visual read did not preserve a soft guard: %+v", output.Events)
 	}
 }
 
@@ -407,7 +469,7 @@ func TestCloudAgentVisionHasPerRunInspectionBudget(t *testing.T) {
 	}
 }
 
-func TestCloudAgentVisionBudgetStopsRunBeforeAnotherModelStep(t *testing.T) {
+func TestCloudAgentVisionBudgetSoftNudgesBeforeAnotherModelStep(t *testing.T) {
 	s, _, _ := cloudAgentVisionFixture(t)
 	req := agentTestRequest()
 	req.VisionEnabled = true
@@ -447,8 +509,16 @@ func TestCloudAgentVisionBudgetStopsRunBeforeAnotherModelStep(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if output.Status != "failed" || !strings.Contains(output.FailureMessage, "识图调用已达到安全上限") {
-		t.Fatalf("inspection budget did not terminate the run: %+v", output)
+	if output.Status != "running" {
+		t.Fatalf("inspection budget terminated the run: %+v", output)
+	}
+	hasGuard, hasFailure := false, false
+	for _, event := range output.Events {
+		hasGuard = hasGuard || event.Type == "read_loop_guard"
+		hasFailure = hasFailure || event.Type == "run_failed"
+	}
+	if !hasGuard || hasFailure {
+		t.Fatalf("inspection budget did not soft-nudge the next model request: %+v", output.Events)
 	}
 }