feat: MLX /status API 통합 — GPU 무접촉 부하 측정

- model_adapter.status_check(): GET /status, 미지원 백엔드는 None
- backend_registry.get_load_status(): /status API 1순위, hybrid fallback
  - active_jobs >=4 매우 바쁨, >=2 바쁨, =1 보통, =0 여유
  - source: status_api | hybrid 표시
- worker._build_system_status(): source별 분기, active_jobs/total_requests 표시
- hybrid 경로의 self-job 제외 (active > 1)
- health loop에서 status도 같이 캐시 (지원 백엔드만)

Mac mini /opt/mlx-proxy.py에 active_jobs 카운터 + /status 엔드포인트 추가됨

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

nanoclaude/services/backend_registry.py

@@ -72,6 +72,8 @@ class BackendRegistry:
         self._sample_count: dict[str, int] = {}
         self._inference_latency: dict[str, float | None] = {}
         self._inference_latency_at: dict[str, float] = {}
+        self._status_cache: dict[str, dict | None] = {}
+        self._status_cached_at: dict[str, float] = {}
         self._measure_lock = asyncio.Lock()
         self._health_task: asyncio.Task | None = None
 
@@ -118,6 +120,10 @@ class BackendRegistry:
             self._latency[role] = elapsed
             if healthy:
                 self._update_baseline(role, elapsed)
+                # /status 같이 캐시 (지원하는 백엔드만)
+                status_data = await adapter.status_check()
+                self._status_cache[role] = status_data
+                self._status_cached_at[role] = time.time()
             if prev != healthy:
                 status = "UP" if healthy else "DOWN"
                 logger.warning("%s (%s) → %s (%.0fms)", adapter.name, role, status, elapsed)
@@ -150,9 +156,46 @@ class BackendRegistry:
             return None
 
     async def get_load_status(self, role: str, force_measure: bool = False) -> dict:
-        """role의 부하 상태 판단. inference latency는 캐시 또는 조건부 측정."""
+        """role의 부하 상태 판단. /status API 우선, 없으면 hybrid (health baseline + 조건부 ping)."""
         health_latency = self._latency.get(role, 0)
         baseline = self._health_baseline.get(role, 50)
+        adapter = self.classifier if role == "classifier" else self.reasoner
+
+        # === 1순위: /status API (GPU 무접촉) ===
+        # force_measure 시 fresh 호출, 아니면 캐시 사용
+        status_data = None
+        if force_measure and adapter:
+            status_data = await adapter.status_check()
+            if status_data:
+                self._status_cache[role] = status_data
+                self._status_cached_at[role] = time.time()
+        else:
+            status_data = self._status_cache.get(role)
+
+        if status_data is not None:
+            active_jobs = status_data.get("active_jobs", 0)
+            # 부드러운 임계치
+            if active_jobs >= 4:
+                load = "매우 바쁨"
+            elif active_jobs >= 2:
+                load = "바쁨"
+            elif active_jobs == 1:
+                load = "보통"
+            else:
+                load = "여유"
+
+            return {
+                "load": load,
+                "source": "status_api",
+                "active_jobs": active_jobs,
+                "total_requests": status_data.get("total_requests", 0),
+                "health_ms": health_latency,
+                "health_baseline_ms": round(baseline, 1),
+                "inference_ms": None,
+                "measured": False,
+            }
+
+        # === 2순위: hybrid fallback (status 미지원 백엔드) ===
         cached_inference = self._inference_latency.get(role)
         cached_at = self._inference_latency_at.get(role, 0)
 
@@ -160,7 +203,6 @@ class BackendRegistry:
         cache_valid = (now - cached_at) < 30
         cooldown_active = (now - cached_at) < 10
 
-        # 조건부 측정 (상대값 + 쿨다운)
         should_measure = False
         if force_measure and not cooldown_active:
             should_measure = True
@@ -173,7 +215,6 @@ class BackendRegistry:
         else:
             inference_latency = cached_inference if cache_valid else None
 
-        # 부하 판단 (inference 우선, health는 fallback)
         if inference_latency is not None and inference_latency > 8000:
             load = "매우 바쁨"
         elif inference_latency is not None and inference_latency > 4000:
@@ -185,20 +226,23 @@ class BackendRegistry:
         else:
             load = "여유"
 
-        # local queue로 보조 판단 (한 단계 상향)
+        # local queue 보조 판단 (자기 자신 제외 — active > 1)
         try:
             from services import job_queue as jq_module
             if jq_module.job_queue:
                 active = jq_module.job_queue.stats.get("active", 0)
-                if active > 0 and load == "보통":
+                if active > 1 and load == "보통":
                     load = "바쁨"
-                elif active > 0 and load == "여유":
+                elif active > 1 and load == "여유":
                     load = "보통"
         except Exception:
             pass
 
         return {
             "load": load,
+            "source": "hybrid",
+            "active_jobs": None,
+            "total_requests": None,
             "health_ms": health_latency,
             "health_baseline_ms": round(baseline, 1),
             "inference_ms": inference_latency,