autoresearch iter 9: drop always-nil error results from task log loaders

loadTaskExecutionLog and loadTaskExecutionLogs could never fail, yet four
call sites branched on their error as if they could, presenting unreachable
code as error handling.

backend/plugins/domain/admin/repository/task.go

@@ -82,9 +82,7 @@ func GetTaskExecutionByTaskID(ctx context.Context, taskID string) (*model.TaskEx
 	if err := GetDB(ctx).Where("task_id = ?", taskID).First(&execution).Error; err != nil {
 		return nil, err
 	}
-	if err := loadTaskExecutionLog(ctx, &execution); err != nil {
+	loadTaskExecutionLog(ctx, &execution)
-		return nil, err
-	}
 	return &execution, nil
 }
 
@@ -94,9 +92,7 @@ func GetTaskExecutionByID(ctx context.Context, id uint64) (*model.TaskExecution,
 	if err := GetDB(ctx).Where("id = ?", id).First(&execution).Error; err != nil {
 		return nil, err
 	}
-	if err := loadTaskExecutionLog(ctx, &execution); err != nil {
+	loadTaskExecutionLog(ctx, &execution)
-		return nil, err
-	}
 	return &execution, nil
 }
 
@@ -108,9 +104,7 @@ func GetLatestTaskExecutionByTaskType(ctx context.Context, taskType string) (*mo
 		Order("id DESC").
 		First(&execution).Error
 	if err == nil {
-		if loadErr := loadTaskExecutionLog(ctx, &execution); loadErr != nil {
+		loadTaskExecutionLog(ctx, &execution)
-			return nil, false, loadErr
-		}
 		return &execution, true, nil
 	}
 	if errors.Is(err, gorm.ErrRecordNotFound) {
@@ -206,9 +200,7 @@ func ListTaskExecutionRecords(ctx context.Context, req model.ListTaskExecutionsR
 	if err := query.Order("id DESC").Offset(offset).Limit(req.PageSize).Find(&executions).Error; err != nil {
 		return nil, 0, err
 	}
-	if err := loadTaskExecutionLogs(ctx, executions); err != nil {
+	loadTaskExecutionLogs(ctx, executions)
-		return nil, 0, err
-	}
 
 	return executions, total, nil
 }
@@ -302,23 +294,25 @@ func TaskExecutionLogRedisKey(taskID string) string {
 	return taskExecutionLogRedisKeyPrefix + taskID
 }
 
-func loadTaskExecutionLog(ctx context.Context, execution *model.TaskExecution) error {
+// loadTaskExecutionLog best-effort enriches an execution with its cached log;
+// a cache miss or failure simply leaves the stored log column in place.
+func loadTaskExecutionLog(ctx context.Context, execution *model.TaskExecution) {
 	cacheSvc := GetCache(ctx)
 	if cacheSvc == nil {
-		return nil
+		return
 	}
 
 	var logText string
 	if err := cacheSvc.Get(ctx, TaskExecutionLogRedisKey(execution.TaskID), &logText); err == nil && logText != "" {
 		execution.Log = logText
 	}
-	return nil
 }
 
-func loadTaskExecutionLogs(ctx context.Context, executions []model.TaskExecution) error {
+// loadTaskExecutionLogs best-effort enriches every execution with its cached log.
+func loadTaskExecutionLogs(ctx context.Context, executions []model.TaskExecution) {
 	cacheSvc := GetCache(ctx)
 	if cacheSvc == nil || len(executions) == 0 {
-		return nil
+		return
 	}
 
 	for i := range executions {
@@ -327,5 +321,4 @@ func loadTaskExecutionLogs(ctx context.Context, executions []model.TaskExecution
 			executions[i].Log = logText
 		}
 	}
-	return nil
 }