refactor(runner): 收敛上游失败决策与轮转策略

将同平台重试、跨平台动作、健康副作用和冷却排队统一到单一失败决策，避免旧降级策略与 failover 重复执行。\n\n增加事务级单源保护、候选实时刷新、冷却错误契约、管理接口严格校验及兼容策略只读展示。\n\n验证：真实 Gateway HTTP/PostgreSQL 接受测试 10 项通过；go test ./...、pnpm openapi、pnpm lint、pnpm test、pnpm build 均通过。

apps/api/internal/store/tasks_runtime.go

@@ -470,6 +470,13 @@ func (s *Store) RequeueTask(ctx context.Context, taskID string, executionToken s
 		delay = 10 * time.Minute
 	}
 	nextRunAt := time.Now().Add(delay)
+	return s.RequeueTaskUntil(ctx, taskID, executionToken, nextRunAt, queueKey)
+}
+
+func (s *Store) RequeueTaskUntil(ctx context.Context, taskID string, executionToken string, nextRunAt time.Time, queueKey string) (GatewayTask, error) {
+	if nextRunAt.Before(time.Now().Add(time.Second)) {
+		nextRunAt = time.Now().Add(time.Second)
+	}
 	return scanGatewayTask(s.pool.QueryRow(ctx, `
 UPDATE gateway_tasks
 SET status = 'queued',
@@ -820,6 +827,29 @@ ORDER BY COALESCE(attempt_no, 0), created_at`, taskID)
 }
 
 func (s *Store) AppendTaskAttemptTrace(ctx context.Context, taskID string, attemptNo int, entry map[string]any) error {
+	if strings.TrimSpace(taskID) == "" || attemptNo <= 0 || len(entry) == 0 {
+		return nil
+	}
+	encoded, err := json.Marshal(entry)
+	if err != nil {
+		return err
+	}
+	result, err := s.pool.Exec(ctx, `
+UPDATE gateway_task_attempts
+SET metrics = jsonb_set(
+      COALESCE(metrics, '{}'::jsonb),
+      '{trace}',
+      COALESCE(metrics->'trace', '[]'::jsonb) || jsonb_build_array($3::jsonb),
+      true
+    )
+WHERE task_id = $1::uuid
+  AND attempt_no = $2::int`, taskID, attemptNo, encoded)
+	if err != nil {
+		return err
+	}
+	if result.RowsAffected() == 0 {
+		return pgx.ErrNoRows
+	}
 	return nil
 }