feat: AI VM stack (WP-12) and Alloy telemetry on k8s, legacy and DB VMs (WP-15)

WP-12(실험 설계서 6장) vm/ai-env: apply.sh(시크릿 4종을 Secret Manager에서 파일로, 미등록이면
성능 저하 모드로 기동), compose(agent 8080·hitl 8081·rag-db pgvector 0.8.7-pg16), ai.env(Discord
서버 Selfheal Lab 1557424985793101824, approvals 1557425140302872698, escalation 1557425282363691048,
OPENAI_MODEL gpt-6.1-sol 후보), 프롬프트 3종, 러너북 11종(조치별·토폴로지·3층 절차).

WP-15(실험 설계서 4.1·4.3): apps/alloy.yaml(Alloy Helm 1.13.0 DaemonSet, 클러스터링으로 KSM·Argo CD·
cadvisor 스크랩 분산, demo 등 파드 로그 → Loki), apps/kube-state-metrics.yaml(Helm 8.6.0).
legacy-api compose에 Alloy 사이드카(up{job="legacy-api"}, 컨테이너 로그). DB VM은
vm/postgres-common/alloy.sh로 apt 설치 + prometheus.exporter.postgres(pg_replication_lag_seconds)
+ custom query pg_is_wal_replay_paused + PostgreSQL 로그.

vm/harness/apply.sh: 준비 대기 루프의 curl에 || true(러너 재기동 순간 curl 56으로 중단되던 문제,
2026-10-08 harness-sync 실측).

vm/ai-env/runbooks/db-primary-down.md

@@ -0,0 +1,5 @@
+# db_primary_down: primary unreachable (layer 3)
+
+Symptoms: probe_success{target="db-primary"} = 0, api 5xx on /api/orders and /api/price, legacy-api logs show connection refused or timeout to 10.20.0.20:5432.
+
+Decision tree for the human: 1) Is the VM RUNNING and only PostgreSQL down? Restart PostgreSQL on the primary (service restart; layer 1 systemd handles crashes). 2) Is the VM stopped or lost? gce.instance_reset or recreate through Terraform. 3) Only if the primary cannot come back: promote the replica (`SELECT pg_promote()` on selfheal-db-replica) and switch the application DSN to 10.20.0.21; this is irreversible (timeline fork), the old primary must be re-cloned. The agent must escalate, never propose promotion.