[CLAUDE] PurchaseEvaluation: go han hanh dong "Tu choi" - chi con Duyet hoac Tra lai (UAT anh Kiet S60 14:14)

- Domain policy: xoa MOI transition -> TuChoi o ca 4 policy (NccOnly + NccWithPlan + ForV2Schema + FromDefinition) -> NextPhases het tra TuChoi, nut FE tu bien mat
- Service guard S60: chan targetPhase=TuChoi moi caller ke ca Admin (dung truoc moi branch — spec bo han, khong escape hatch); message huong dan dung Tra lai / Xoa nhap
- FE x2 app: filter phong thu next.filter(p != TuChoi) PeWorkflowPanel (SHA256 identical); dialog/isCancel giu dead-safe de flip lai de
- Enum TuChoi + phieu TuChoi cu + tab filter "Tu choi" GIU display (data cu render binh thuong)
- SlaExpiryJob chi dung Contract — PE khong auto-TuChoi, khong anh huong
- Tests spec-change cung commit: Domain flip BothPolicies_TuChoi_RemovedFromAllTransitions_S60 + NEW V2SchemaPolicy fact; Infra NEW TargetTuChoi_WithRejectDecision_Throws_TuChoiRemoved_S60 (guard #45 test cu giu nguyen PASS — van dung truoc)
- Test 254 -> 256 PASS (59 Domain + 197 Infra)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/SolutionErp.Infrastructure.Tests/Services/PurchaseEvaluationWorkflowServiceGuardTests.cs

@@ -121,6 +121,37 @@ public class PurchaseEvaluationWorkflowServiceGuardTests
         }
     }
 
+    [Fact]
+    public async Task TransitionAsync_TargetTuChoi_WithRejectDecision_Throws_TuChoiRemoved_S60()
+    {
+        // UAT S60 (anh Kiệt 14:14): "bỏ luôn nút Từ chối — Duyệt hoặc Trả về
+        // thôi". Payload TuChoi + decision=Reject (hợp lệ THEO SPEC CŨ) giờ bị
+        // guard S60 chặn hẳn — TuChoi hết đường vào từ transition API (guard
+        // #45 decision-mismatch vẫn đứng trước cover nhánh TuChoi+Approve).
+        var (svc, fix, db) = CreateService();
+        using (fix)
+        {
+            var pe = BuildPeInChoDuyet("PE-GUARD-004");
+            db.PurchaseEvaluations.Add(pe);
+            await db.SaveChangesAsync(CancellationToken.None);
+
+            var act = async () => await svc.TransitionAsync(
+                evaluation: pe,
+                targetPhase: PurchaseEvaluationPhase.TuChoi,
+                actorUserId: Guid.NewGuid(),
+                actorRoles: new[] { AppRoles.CostControl },
+                decision: ApprovalDecision.Reject,
+                comment: "test tu choi removed S60",
+                ct: CancellationToken.None);
+
+            await act.Should().ThrowAsync<ConflictException>()
+                .WithMessage("*Từ chối*đã được gỡ*");
+
+            pe.Phase.Should().Be(PurchaseEvaluationPhase.ChoDuyet,
+                "Guard chặn trước khi mutate — phiếu giữ nguyên ChoDuyet");
+        }
+    }
+
     [Fact]
     public async Task TransitionAsync_TargetTraLai_WithRejectDecision_SetsPhaseTraLai()
     {