Add eval harness (#62 P4), status frames (#96), and agentic runs (#63).

Ship the Phase 4 accuracy eval suite with a manual Gitea workflow, emit
versioned WS status frames during grounded chat, and introduce opt-in
agent infrastructure (Redis/Celery, AgentRun/Step, tools, orchestrator)
gated by ALLOW_AGENTIC_TASKS so default chat behaviour stays unchanged.

docker-compose.prod.yml

@@ -12,5 +12,17 @@ services:
       # Chroma vector index only (uploaded file blobs live in Postgres).
       - chroma_data:/app/llm_be/chroma_db
 
+  # Celery worker for long-running agent tasks (#63). Only started when the
+  # `agentic` profile is enabled and REDIS_URL/CELERY_BROKER_URL are set in
+  # .env (control-node secret) — points at a shared Redis instance, no
+  # bundled `redis` service here (mirrors the "no bundled Postgres" policy).
+  worker:
+    build: .
+    profiles: ["agentic"]
+    restart: unless-stopped
+    command: ["uv", "run", "celery", "-A", "llm_be", "worker", "--loglevel=info"]
+    env_file:
+      - .env
+
 volumes:
   chroma_data: