fix: 修复 CI 检查失败

- gofmt: 修复 error_passthrough_service.go 格式问题
- errcheck: 修复 error_passthrough_runtime_test.go 类型断言未检查
- staticcheck: if-else 改为 switch (gateway_service.go)
- test: 修复两个测试用例错误使用 MODEL_CAPACITY_EXHAUSTED 导致走错路径

backend/internal/service/antigravity_single_account_retry_test.go

@@ -153,13 +153,14 @@ func TestHandleSmartRetry_503_LongDelay_NoSingleAccountRetry_StillSwitches(t *te
 		Platform: PlatformAntigravity,
 	}
 
-	// 503 + 39s >= 7s 阈值
+	// 503 + 39s >= 7s 阈值（使用 RATE_LIMIT_EXCEEDED 而非 MODEL_CAPACITY_EXHAUSTED，
+	// 因为 MODEL_CAPACITY_EXHAUSTED 走独立的重试路径，不触发 shouldRateLimitModel）
 	respBody := []byte(`{
 		"error": {
 			"code": 503,
-			"status": "UNAVAILABLE",
+			"status": "RESOURCE_EXHAUSTED",
 			"details": [
-				{"@type": "type.googleapis.com/google.rpc.ErrorInfo", "metadata": {"model": "gemini-3-pro-high"}, "reason": "MODEL_CAPACITY_EXHAUSTED"},
+				{"@type": "type.googleapis.com/google.rpc.ErrorInfo", "metadata": {"model": "gemini-3-pro-high"}, "reason": "RATE_LIMIT_EXCEEDED"},
 				{"@type": "type.googleapis.com/google.rpc.RetryInfo", "retryDelay": "39s"}
 			]
 		}
@@ -339,13 +340,14 @@ func TestHandleSmartRetry_503_ShortDelay_SingleAccountRetry_NoRateLimit(t *testi
 
 // TestHandleSmartRetry_503_ShortDelay_NoSingleAccountRetry_SetsRateLimit
 // 对照组：503 + retryDelay < 7s + 无 SingleAccountRetry → 智能重试耗尽后照常设限流
+// 使用 RATE_LIMIT_EXCEEDED 而非 MODEL_CAPACITY_EXHAUSTED，因为后者走独立的 60 次重试路径
 func TestHandleSmartRetry_503_ShortDelay_NoSingleAccountRetry_SetsRateLimit(t *testing.T) {
 	failRespBody := `{
 		"error": {
 			"code": 503,
-			"status": "UNAVAILABLE",
+			"status": "RESOURCE_EXHAUSTED",
 			"details": [
-				{"@type": "type.googleapis.com/google.rpc.ErrorInfo", "metadata": {"model": "gemini-3-flash"}, "reason": "MODEL_CAPACITY_EXHAUSTED"},
+				{"@type": "type.googleapis.com/google.rpc.ErrorInfo", "metadata": {"model": "gemini-3-flash"}, "reason": "RATE_LIMIT_EXCEEDED"},
 				{"@type": "type.googleapis.com/google.rpc.RetryInfo", "retryDelay": "0.1s"}
 			]
 		}
@@ -371,9 +373,9 @@ func TestHandleSmartRetry_503_ShortDelay_NoSingleAccountRetry_SetsRateLimit(t *t
 	respBody := []byte(`{
 		"error": {
 			"code": 503,
-			"status": "UNAVAILABLE",
+			"status": "RESOURCE_EXHAUSTED",
 			"details": [
-				{"@type": "type.googleapis.com/google.rpc.ErrorInfo", "metadata": {"model": "gemini-3-flash"}, "reason": "MODEL_CAPACITY_EXHAUSTED"},
+				{"@type": "type.googleapis.com/google.rpc.ErrorInfo", "metadata": {"model": "gemini-3-flash"}, "reason": "RATE_LIMIT_EXCEEDED"},
 				{"@type": "type.googleapis.com/google.rpc.RetryInfo", "retryDelay": "0.1s"}
 			]
 		}

backend/internal/service/error_passthrough_runtime_test.go

@@ -219,7 +219,9 @@ func TestApplyErrorPassthroughRule_SkipMonitoringSetsContextKey(t *testing.T) {
 	assert.True(t, matched)
 	v, exists := c.Get(OpsSkipPassthroughKey)
 	assert.True(t, exists, "OpsSkipPassthroughKey should be set when skip_monitoring=true")
-	assert.True(t, v.(bool))
+	boolVal, ok := v.(bool)
+	assert.True(t, ok, "value should be bool")
+	assert.True(t, boolVal)
 }
 
 func TestApplyErrorPassthroughRule_NoSkipMonitoringDoesNotSetContextKey(t *testing.T) {

backend/internal/service/error_passthrough_service.go

@@ -161,7 +161,7 @@ func (s *ErrorPassthroughService) MatchRule(platform string, statusCode int, bod
 	}
 
 	lowerPlatform := strings.ToLower(platform)
-	var bodyLower string     // 延迟初始化，只在需要关键词匹配时计算
+	var bodyLower string // 延迟初始化，只在需要关键词匹配时计算
 	var bodyLowerDone bool
 
 	for _, rule := range rules {

backend/internal/service/gateway_service.go

@@ -385,9 +385,10 @@ func (s *GatewayService) TempUnscheduleRetryableError(ctx context.Context, accou
 		return
 	}
 	// 根据状态码选择封禁策略
-	if failoverErr.StatusCode == http.StatusBadRequest {
+	switch failoverErr.StatusCode {
+	case http.StatusBadRequest:
 		tempUnscheduleGoogleConfigError(ctx, s.accountRepo, accountID, "[handler]")
-	} else if failoverErr.StatusCode == http.StatusBadGateway {
+	case http.StatusBadGateway:
 		tempUnscheduleEmptyResponse(ctx, s.accountRepo, accountID, "[handler]")
 	}
 }