host-metrics: stack.yml + compose skeleton

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

stack_orchestrator/data/compose/docker-compose-host-metrics.yml

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+services:
+  telegraf:
+    image: telegraf:1.36
+    restart: unless-stopped
+    network_mode: host
+    pid: host
+    entrypoint: ["/scripts/telegraf-entrypoint.sh"]
+    environment:
+      INFLUXDB_URL: ${INFLUXDB_URL}
+      INFLUXDB_DB: ${INFLUXDB_DB:-host_metrics}
+      INFLUXDB_USER: ${INFLUXDB_WRITE_USER}
+      INFLUXDB_PASSWORD: ${INFLUXDB_WRITE_PASSWORD}
+      COLLECT_INTERVAL: ${COLLECT_INTERVAL:-10s}
+      HOST_TAG: ${HOST_TAG:-}
+      COLLECT_ZFS: ${COLLECT_ZFS:-false}
+    volumes:
+      - ../config/host-metrics/telegraf.conf.tpl:/etc/telegraf/telegraf.conf.tpl:ro
+      - ../config/host-metrics/scripts/telegraf-entrypoint.sh:/scripts/telegraf-entrypoint.sh:ro
+      - /proc:/hostfs/proc:ro
+      - /sys:/hostfs/sys:ro
+      - /:/hostfs:ro

stack_orchestrator/data/stacks/host-metrics/README.md

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+# host-metrics stack
+
+Per-host system metrics collector. Runs telegraf with host networking, host
+PID namespace, and read-only bind mounts of /proc, /sys, and / so it can
+report real CPU, memory, disk, network, and process metrics for the machine
+it runs on. Writes to an InfluxDB 1.x endpoint of your choosing.
+
+Deploy one instance per machine you want monitored.
+
+## Quick deploy
+
+(Filled in by a later task.)

stack_orchestrator/data/stacks/host-metrics/stack.yml

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+version: "1.1"
+name: host-metrics
+description: "Per-host system metrics collector (telegraf -> InfluxDB)"
+pods:
+  - host-metrics