fix(risk): fix circuit_breaker position_limit_zero_portfolio test

Replace RealBrokerClient (which connects to localhost:50054) with
MockBrokerService in test, so it runs without a live broker. All 209
risk tests now pass.

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

risk/src/circuit_breaker.rs

@@ -798,6 +798,36 @@ mod tests {
     use tokio;
     // CANONICAL TYPE IMPORTS - Use types::prelude for dec! macro
 
+    /// Mock broker service for unit tests that don't require a real broker connection
+    struct MockBrokerService {
+        portfolio_value: Decimal,
+        daily_pnl: Decimal,
+    }
+
+    impl MockBrokerService {
+        fn with_zero_portfolio() -> Self {
+            Self {
+                portfolio_value: Decimal::ZERO,
+                daily_pnl: Decimal::ZERO,
+            }
+        }
+    }
+
+    #[async_trait]
+    impl BrokerAccountService for MockBrokerService {
+        async fn get_portfolio_value(&self, _account_id: &str) -> RiskResult<Decimal> {
+            Ok(self.portfolio_value)
+        }
+
+        async fn get_daily_pnl(&self, _account_id: &str) -> RiskResult<Decimal> {
+            Ok(self.daily_pnl)
+        }
+
+        async fn get_positions(&self, _account_id: &str) -> RiskResult<Vec<Position>> {
+            Ok(Vec::new())
+        }
+    }
+
     fn create_test_config() -> Result<CircuitBreakerConfig, Box<dyn std::error::Error>> {
         Ok(CircuitBreakerConfig {
             enabled: true,
@@ -876,7 +906,8 @@ mod tests {
     async fn test_circuit_breaker_position_limit_zero_portfolio(
     ) -> Result<(), Box<dyn std::error::Error>> {
         let config = create_test_config()?;
-        let broker_service = Arc::new(RealBrokerClient::new("http://localhost:50054".to_string()));
+        let broker_service: Arc<dyn BrokerAccountService> =
+            Arc::new(MockBrokerService::with_zero_portfolio());
 
         if let Ok(circuit_breaker) = RealCircuitBreaker::new(config, broker_service).await {
             let account_id = "TEST_ACCOUNT";