P3.1: GPU/Queue-aware routing — NCS metrics + scoring-based model selection

NCS (services/node-capabilities/metrics.py):
- NodeLoad: inflight_jobs, queue_depth, concurrency_limit, estimated_wait_ms,
  cpu_load_1m, mem_pressure (macOS + Linux), rtt_ms_to_hub
- RuntimeLoad: per-runtime healthy, p50_ms, p95_ms from rolling 50-sample window
- POST /capabilities/report_latency for node-worker → NCS reporting
- NCS fetches worker metrics via NODE_WORKER_URL

Node Worker:
- GET /metrics endpoint (inflight, concurrency, latency buffers)
- Latency tracking per job type (llm/vision) with rolling buffer
- Fire-and-forget latency reporting to NCS after each successful job

Router (model_select v3):
- score_candidate(): wait + model_latency + cross_node_penalty + prefer_bonus
- LOCAL_THRESHOLD_MS=250: prefer local if within threshold of remote
- ModelSelection.score field for observability
- Structured [score] logs with chosen node, model, and score breakdown

Tests: 19 new (12 scoring + 7 NCS metrics), 36 total pass
Docs: ops/runbook_p3_1.md, ops/CHANGELOG_FABRIC.md

No breaking changes to JobRequest/JobResponse or capabilities schema.

Made-with: Cursor

docker-compose.node2-sofiia.yml

@@ -126,6 +126,7 @@ services:
       - CACHE_TTL_SEC=15
       - ENABLE_NATS_CAPS=true
       - NATS_URL=nats://dagi-nats:4222
+      - NODE_WORKER_URL=http://node-worker:8109
     depends_on:
       - swapper-service
       - dagi-nats
@@ -150,6 +151,7 @@ services:
       - NODE_DEFAULT_LLM=qwen3:14b
       - NODE_DEFAULT_VISION=llava:13b
       - NODE_WORKER_MAX_CONCURRENCY=2
+      - NCS_REPORT_URL=http://node-capabilities:8099
     depends_on:
       - dagi-nats
       - swapper-service