fix(v2): settle 定位尝试的瞬时读库错误归 SettleFailed(可重试),不再误标 not_found

AttemptByProviderRef 返回非哨兵错误(如 DB 抖动)时原先与"查无此单"终态
一并标 SettleNotFound;调用方按结果值决定 ack,会把已付订单永久丢弃。
非哨兵分支改判 SettleFailed(可重试,渠道会重投),errors.Is(ErrAttemptNotFound)
分支维持 SettleNotFound 不变。新增 TestSettleTransientReadErrorIsFailed 通过
关闭底层连接强制产出瞬时读库错误,验证结果与语义。

internal/gateway/settle.go

@@ -43,7 +43,8 @@ func (g *Gateway) Settle(ctx context.Context, ev *provider.PaidEvent) (SettleRes
 		if errors.Is(err, store.ErrAttemptNotFound) {
 			return SettleNotFound, nil
 		}
-		return SettleNotFound, err
+		// 读库瞬时失败是可重试态,不能与"查无此单"终态混淆。
+		return SettleFailed, err
 	}
 	// 金额/币种核对:币种须一致,实付须 ≥ 应收(允许 crypto 多付,拒少付)。
 	if ev.PaidCurrency != att.Currency || ev.PaidAmountMinor < att.AmountMinor {

internal/gateway/settle_test.go

@@ -5,9 +5,13 @@ import (
 	"encoding/json"
 	"testing"
 
+	"github.com/wangjia/pay/config"
+	"github.com/wangjia/pay/internal/accounts"
 	"github.com/wangjia/pay/internal/gateway"
 	"github.com/wangjia/pay/internal/model"
 	"github.com/wangjia/pay/internal/provider"
+	"github.com/wangjia/pay/internal/provider/fake"
+	"github.com/wangjia/pay/internal/store"
 )
 
 func attemptRef(t *testing.T, orders interface {
@@ -103,6 +107,41 @@ func TestSettleEnqueueFailureKeepsOrderPending(t *testing.T) {
 	}
 }
 
+// 瞬时读库失败(非 store.ErrAttemptNotFound 哨兵)必须归 SettleFailed(可重试),
+// 不能与"查无此单"的终态 SettleNotFound 混淆——否则调用方按结果值决定 ack,
+// 会把已付订单永久丢弃。构造方式:先建好订单/尝试,再直接关掉底层连接,
+// 让 AttemptByProviderRef 打到一个已关闭的 DB 上,产出非哨兵错误。
+func TestSettleTransientReadErrorIsFailed(t *testing.T) {
+	db := model.OpenTestDB(t)
+	orders := store.NewOrderStore(db)
+	preg := provider.NewRegistry()
+	fp := fake.New()
+	preg.Register(fp)
+	areg := accounts.New([]config.AccountConfig{
+		{AccountID: "fake-a1", Channel: "fake", Region: "global", Enabled: true, Weight: 1},
+	})
+	spy := &spyEnqueuer{}
+	g := gateway.New(orders, preg, areg, stubResolver{}, spy, "global")
+
+	ctx := context.Background()
+	g.CreateOrder(ctx, gateway.CreateOrderInput{SKU: "pro_year", Method: "fake", BizSystem: "pangolin", BizRef: "u-1"})
+	ref := attemptRef(t, orders)
+
+	sqlDB, err := db.DB()
+	if err != nil {
+		t.Fatalf("db.DB(): %v", err)
+	}
+	if err := sqlDB.Close(); err != nil {
+		t.Fatalf("close db: %v", err)
+	}
+
+	ev := &provider.PaidEvent{ProviderRef: ref, Status: provider.PaidSucceeded, PaidAmountMinor: 29990000, PaidCurrency: "USDT"}
+	got, err := g.Settle(ctx, ev)
+	if got != gateway.SettleFailed || err == nil {
+		t.Fatalf("瞬时读库失败应 SettleFailed+err, got %v, %v", got, err)
+	}
+}
+
 func TestHandleCallbackAndSync(t *testing.T) {
 	g, fp, _, orders := newGateway(t)
 	ctx := context.Background()