P3.2+P3.3+P3.4: NODA1 node-worker + NATS auth config + Prometheus counters

P3.2 — Multi-node deployment:
- Added node-worker service to docker-compose.node1.yml (NODE_ID=noda1)
- NCS NODA1 now has NODE_WORKER_URL for metrics collection
- Fixed NODE_ID consistency: router NODA1 uses 'noda1'
- NODA2 node-worker/NCS gets NCS_REPORT_URL for latency reporting

P3.3 — NATS accounts/auth (opt-in config):
- config/nats-server.conf with 3 accounts: SYS, FABRIC, APP
- Per-user topic permissions (router, ncs, node_worker)
- Leafnode listener :7422 with auth
- Not yet activated (requires credential provisioning)

P3.4 — Prometheus counters:
- Router /fabric_metrics: caps_refresh, caps_stale, model_select,
  offload_total, breaker_state, score_ms histogram
- Node Worker /prom_metrics: jobs_total, inflight gauge, latency_ms histogram
- NCS /prom_metrics: runtime_health, runtime_p50/p95, node_wait_ms
- All bound to 127.0.0.1 (not externally exposed)

Made-with: Cursor

services/router/fabric_metrics.py

@@ -0,0 +1,82 @@
+"""Prometheus metrics for Fabric routing layer.
+
+Exposed via /fabric_metrics (separate from main /metrics to avoid conflicts).
+Falls back to no-op counters if prometheus_client is not installed.
+"""
+import logging
+import time
+from typing import Optional
+
+logger = logging.getLogger("fabric_metrics")
+
+try:
+    from prometheus_client import Counter, Gauge, Histogram, CollectorRegistry, generate_latest
+    PROM_AVAILABLE = True
+    REGISTRY = CollectorRegistry()
+
+    caps_refresh = Counter(
+        "fabric_caps_refresh_total", "Capabilities refresh attempts",
+        ["status"], registry=REGISTRY,
+    )
+    caps_stale = Counter(
+        "fabric_caps_stale_total", "Stale capabilities used",
+        registry=REGISTRY,
+    )
+    model_select = Counter(
+        "fabric_model_select_total", "Model selection decisions",
+        ["chosen_node", "chosen_runtime", "type"], registry=REGISTRY,
+    )
+    offload_total = Counter(
+        "fabric_offload_total", "Offload attempts",
+        ["status", "node", "type"], registry=REGISTRY,
+    )
+    breaker_state = Gauge(
+        "fabric_breaker_state", "Circuit breaker state (1=open)",
+        ["node", "type"], registry=REGISTRY,
+    )
+    score_hist = Histogram(
+        "fabric_score_ms", "Model selection score distribution",
+        buckets=[100, 250, 500, 1000, 2000, 5000, 10000],
+        registry=REGISTRY,
+    )
+
+except ImportError:
+    PROM_AVAILABLE = False
+    REGISTRY = None
+    logger.info("prometheus_client not installed, fabric metrics disabled")
+
+
+def inc_caps_refresh(status: str):
+    if PROM_AVAILABLE:
+        caps_refresh.labels(status=status).inc()
+
+
+def inc_caps_stale():
+    if PROM_AVAILABLE:
+        caps_stale.inc()
+
+
+def inc_model_select(node: str, runtime: str, req_type: str):
+    if PROM_AVAILABLE:
+        model_select.labels(chosen_node=node, chosen_runtime=runtime, type=req_type).inc()
+
+
+def inc_offload(status: str, node: str, req_type: str):
+    if PROM_AVAILABLE:
+        offload_total.labels(status=status, node=node, type=req_type).inc()
+
+
+def set_breaker(node: str, req_type: str, is_open: bool):
+    if PROM_AVAILABLE:
+        breaker_state.labels(node=node, type=req_type).set(1 if is_open else 0)
+
+
+def observe_score(score: int):
+    if PROM_AVAILABLE:
+        score_hist.observe(score)
+
+
+def get_metrics_text() -> Optional[bytes]:
+    if PROM_AVAILABLE and REGISTRY:
+        return generate_latest(REGISTRY)
+    return None