fix: exclude Antigravity from OAuth 401 temp-unschedulable and escalation logic

PR #723 changed all OAuth 401 to use SetTempUnschedulable instead of SetError,
and PR #761 added 401 escalation logic in tryTempUnschedulable. Both caused
non-OpenAI accounts to frequently become temporarily unschedulable.

- HandleUpstreamError case 401: limit temp-unschedulable to OpenAI OAuth only,
  other platforms (Anthropic/Gemini/Antigravity) revert to original SetError
- tryTempUnschedulable: skip 401 escalation for Antigravity, let its
  applyErrorPolicy temp_unschedulable_rules handle 401 naturally

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/internal/service/error_policy_test.go

@@ -114,7 +114,7 @@ func TestCheckErrorPolicy(t *testing.T) {
 			account: &Account{
 				ID:                      15,
 				Type:                    AccountTypeOAuth,
-				Platform:                PlatformAntigravity,
+				Platform:                PlatformGemini, // 非 Antigravity 平台才有 401 升级逻辑
 				TempUnschedulableReason: `{"status_code":401,"until_unix":1735689600}`,
 				Credentials: map[string]any{
 					"temp_unschedulable_enabled": true,
@@ -131,6 +131,28 @@ func TestCheckErrorPolicy(t *testing.T) {
 			body:       []byte(`unauthorized`),
 			expected:   ErrorPolicyNone,
 		},
+		{
+			name: "temp_unschedulable_401_antigravity_no_escalation",
+			account: &Account{
+				ID:                      16,
+				Type:                    AccountTypeOAuth,
+				Platform:                PlatformAntigravity, // Antigravity 跳过 401 升级，由 rules 正常处理
+				TempUnschedulableReason: `{"status_code":401,"until_unix":1735689600}`,
+				Credentials: map[string]any{
+					"temp_unschedulable_enabled": true,
+					"temp_unschedulable_rules": []any{
+						map[string]any{
+							"error_code":       float64(401),
+							"keywords":         []any{"unauthorized"},
+							"duration_minutes": float64(10),
+						},
+					},
+				},
+			},
+			statusCode: 401,
+			body:       []byte(`unauthorized`),
+			expected:   ErrorPolicyTempUnscheduled, // Antigravity 不升级，继续走规则匹配
+		},
 		{
 			name: "temp_unschedulable_body_miss_returns_none",
 			account: &Account{

backend/internal/service/ratelimit_service.go

@@ -128,8 +128,9 @@ func (s *RateLimitService) HandleUpstreamError(ctx context.Context, account *Acc
 		}
 		// 其他 400 错误（如参数问题）不处理，不禁用账号
 	case 401:
-		// 对所有 OAuth 账号在 401 错误时调用缓存失效并强制下次刷新
-		if account.Type == AccountTypeOAuth {
+		// OpenAI OAuth 账号在 401 错误时临时不可调度（保持 active 让刷新服务恢复）；
+		// 其他平台 OAuth 账号保持原有 SetError 行为（Antigravity 主流程不走此路径）。
+		if account.Type == AccountTypeOAuth && account.Platform == PlatformOpenAI {
 			// 1. 失效缓存
 			if s.tokenCacheInvalidator != nil {
 				if err := s.tokenCacheInvalidator.InvalidateToken(ctx, account); err != nil {
@@ -1093,7 +1094,8 @@ func (s *RateLimitService) tryTempUnschedulable(ctx context.Context, account *Ac
 	}
 	// 401 首次命中可临时不可调度（给 token 刷新窗口）；
 	// 若历史上已因 401 进入过临时不可调度，则本次应升级为 error（返回 false 交由默认错误逻辑处理）。
-	if statusCode == http.StatusUnauthorized {
+	// Antigravity 跳过：其 401 由 applyErrorPolicy 的 temp_unschedulable_rules 自行控制，无需升级逻辑。
+	if statusCode == http.StatusUnauthorized && account.Platform != PlatformAntigravity {
 		reason := account.TempUnschedulableReason
 		// 缓存可能没有 reason，从 DB 回退读取
 		if reason == "" {

backend/internal/service/ratelimit_service_401_db_fallback_test.go

@@ -28,6 +28,7 @@ func (r *dbFallbackRepoStub) GetByID(ctx context.Context, id int64) (*Account, e
 func TestCheckErrorPolicy_401_DBFallback_Escalates(t *testing.T) {
 	// Scenario: cache account has empty TempUnschedulableReason (cache miss),
 	// but DB account has a previous 401 record → should escalate to ErrorPolicyNone.
+	// 注意：Antigravity 跳过 401 升级，此测试使用 Gemini 平台验证升级逻辑。
 	repo := &dbFallbackRepoStub{
 		dbAccount: &Account{
 			ID:                      20,
@@ -39,7 +40,7 @@ func TestCheckErrorPolicy_401_DBFallback_Escalates(t *testing.T) {
 	account := &Account{
 		ID:                      20,
 		Type:                    AccountTypeOAuth,
-		Platform:                PlatformAntigravity,
+		Platform:                PlatformGemini,
 		TempUnschedulableReason: "", // cache miss — reason is empty
 		Credentials: map[string]any{
 			"temp_unschedulable_enabled": true,

backend/internal/service/ratelimit_service_401_test.go

@@ -41,13 +41,37 @@ func (r *tokenCacheInvalidatorRecorder) InvalidateToken(ctx context.Context, acc
 	return r.err
 }
 
-func TestRateLimitService_HandleUpstreamError_OAuth401SetsTempUnschedulable(t *testing.T) {
+// TestRateLimitService_HandleUpstreamError_OpenAIOAuth401SetsTempUnschedulable
+// 仅 OpenAI OAuth 账号 401 使用 temp_unschedulable
+func TestRateLimitService_HandleUpstreamError_OpenAIOAuth401SetsTempUnschedulable(t *testing.T) {
+	repo := &rateLimitAccountRepoStub{}
+	invalidator := &tokenCacheInvalidatorRecorder{}
+	service := NewRateLimitService(repo, nil, &config.Config{}, nil, nil)
+	service.SetTokenCacheInvalidator(invalidator)
+	account := &Account{
+		ID:       100,
+		Platform: PlatformOpenAI,
+		Type:     AccountTypeOAuth,
+	}
+
+	shouldDisable := service.HandleUpstreamError(context.Background(), account, 401, http.Header{}, []byte("unauthorized"))
+
+	require.True(t, shouldDisable)
+	require.Equal(t, 0, repo.setErrorCalls)
+	require.Equal(t, 1, repo.tempCalls)
+	require.Len(t, invalidator.accounts, 1)
+}
+
+// TestRateLimitService_HandleUpstreamError_NonOpenAIOAuth401SetsError
+// 非 OpenAI 的 OAuth 账号 401 走原有 SetError 行为
+func TestRateLimitService_HandleUpstreamError_NonOpenAIOAuth401SetsError(t *testing.T) {
 	tests := []struct {
 		name     string
 		platform string
 	}{
 		{name: "gemini", platform: PlatformGemini},
 		{name: "antigravity", platform: PlatformAntigravity},
+		{name: "anthropic", platform: PlatformAnthropic},
 	}
 
 	for _, tt := range tests {
@@ -60,29 +84,20 @@ func TestRateLimitService_HandleUpstreamError_OAuth401SetsTempUnschedulable(t *t
 				ID:       100,
 				Platform: tt.platform,
 				Type:     AccountTypeOAuth,
-				Credentials: map[string]any{
-					"temp_unschedulable_enabled": true,
-					"temp_unschedulable_rules": []any{
-						map[string]any{
-							"error_code":       401,
-							"keywords":         []any{"unauthorized"},
-							"duration_minutes": 30,
-							"description":      "custom rule",
-						},
-					},
-				},
 			}
 
 			shouldDisable := service.HandleUpstreamError(context.Background(), account, 401, http.Header{}, []byte("unauthorized"))
 
 			require.True(t, shouldDisable)
-			require.Equal(t, 0, repo.setErrorCalls)
-			require.Equal(t, 1, repo.tempCalls)
-			require.Len(t, invalidator.accounts, 1)
+			require.Equal(t, 1, repo.setErrorCalls)
+			require.Equal(t, 0, repo.tempCalls)
+			require.Contains(t, repo.lastErrorMsg, "Authentication failed (401)")
 		})
 	}
 }
 
+// TestRateLimitService_HandleUpstreamError_OAuth401InvalidatorError
+// OpenAI OAuth 401 缓存失效出错时仍走 temp_unschedulable
 func TestRateLimitService_HandleUpstreamError_OAuth401InvalidatorError(t *testing.T) {
 	repo := &rateLimitAccountRepoStub{}
 	invalidator := &tokenCacheInvalidatorRecorder{err: errors.New("boom")}
@@ -90,7 +105,7 @@ func TestRateLimitService_HandleUpstreamError_OAuth401InvalidatorError(t *testin
 	service.SetTokenCacheInvalidator(invalidator)
 	account := &Account{
 		ID:       101,
-		Platform: PlatformGemini,
+		Platform: PlatformOpenAI,
 		Type:     AccountTypeOAuth,
 	}