refactor(ml): implement CircuitBreakerTrait for ML circuit breaker

Bridge the ML crate's parking_lot::RwLock-based CircuitBreaker to the
shared CircuitBreakerTrait from common. Maps synchronous methods
(allow_request, record_success, etc.) to the async trait interface and
converts CircuitState variants to common::CircuitBreakerState.

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

ml/src/common/circuit_breaker.rs

@@ -8,6 +8,9 @@ use std::sync::atomic::{AtomicU32, AtomicU64, Ordering};
 use std::sync::Arc;
 use std::time::{Duration, Instant};
 
+use ::common::resilience::circuit_breaker::{
+    CircuitBreakerState as CommonCBState, CircuitBreakerTrait,
+};
 use parking_lot::RwLock;
 use tracing::{debug, info, warn};
 
@@ -253,6 +256,33 @@ impl CircuitBreaker {
     }
 }
 
+#[async_trait::async_trait]
+impl CircuitBreakerTrait for CircuitBreaker {
+    async fn can_execute(&self) -> bool {
+        self.allow_request()
+    }
+
+    async fn record_success(&self) {
+        CircuitBreaker::record_success(self);
+    }
+
+    async fn record_failure(&self) {
+        CircuitBreaker::record_failure(self);
+    }
+
+    async fn state(&self) -> CommonCBState {
+        match self.current_state() {
+            CircuitState::Closed => CommonCBState::Closed,
+            CircuitState::Open => CommonCBState::Open,
+            CircuitState::HalfOpen => CommonCBState::HalfOpen,
+        }
+    }
+
+    async fn reset(&self) {
+        CircuitBreaker::reset(self);
+    }
+}
+
 /// Circuit breaker statistics
 #[derive(Debug, Clone)]
 pub struct CircuitBreakerStats {