feat(rank6): node-exporter renders from a template; guard chain is one snippet

- service-map render node-exporter-unit --host H: the MIRROR pair comment
  ('keep this file in step') becomes a template. Per-host title, LAN
  address from the hosts map, port from the node-<host> scrape job. Both
  tracked quadlets are now rendered artifacts; check_drift gates them.
- dankclaw/Caddyfile: the nine verbatim Anubis pre-auth chains
  (reverse_proxy anubis:8923 + X-Real-Ip) collapse into the (guarded)
  named snippet; guarded vhosts are 'import guarded'. Validated with real
  caddy 2.11.7 (import resolution clean; the stock image stops at the
  porkbun module and the git basicauth placeholder, as designed).
- vhost-scoped guard greps (authentik, homepage_caddy, marreta_quadlet)
  now pin 'import guarded' in the vhost block.
- Service Inventory + Authentik docs carry the new laws.

scripts/service-map.py

@@ -100,6 +100,12 @@ class Inventory:
                 return str(host["dns_edge"])
         raise SystemExit(f"{self.origin}: no host declares dns_edge")
 
+    def service(self, name: str) -> dict | None:
+        for svc in self.services:
+            if svc["name"] == name:
+                return svc
+        return None
+
     def unit_dirs(self, svc: dict[str, Any], host: str | None = None) -> list[str]:
         """The repo dirs holding this service's unit files, for one host."""
         dirs = svc.get("unit_dir")
@@ -492,6 +498,85 @@ def check_config(inv: Inventory) -> list[str]:
     return problems
 
 
+# --- node-exporter quadlet template (rank 6) --------------------------------
+# The two node-exporter units were a MIRROR pair kept in step by a comment.
+# The template is now the law; `check` drift-gates both tracked copies.
+NODE_EXPORTER_TEMPLATE = """\
+# Quadlet unit: node-exporter (rootless, boot-persistent) — RENDERED ARTIFACT.
+# Regenerate: python3 scripts/service-map.py render node-exporter-unit --host {host}
+# Source: shared/services.yml (entry node-exporter) + this template.
+#
+# Install path on {host}: ~/.config/containers/systemd/node-exporter.container
+# Unit name: node-exporter.service (container name: node-exporter)
+#
+# Host metrics source for Prometheus. Replaces the compose service of the same
+# name (the "Observability" block): Dankclaw moved to this quadlet on
+# 2026-09-11, Dankserver on 2026-09-16 — its compose-only copy died at a reboot
+# and stayed dead (rootless Podman does not restart bare containers after the
+# explicit stop shutdown performs), dead for a day and a half before anyone
+# noticed. One owner per container name; no compose file remains anywhere.
+#
+# HOST NAMESPACE. It must run in the host network namespace to report the
+# host's own interfaces/connections, and --pid=host for the processes and
+# cgroups collectors. "localhost" inside the container is therefore the host's
+# loopback, which is what the homepage status timer probes.
+#
+# LISTEN ADDRESSES. Exactly two: loopback for the homepage status probe, and
+# the LAN address, because Prometheus — which runs in a container on
+# dankclaw_default — scrapes http://{lan}:{port}/metrics
+# (shared/prometheus/prometheus.yml, job "node-{host}"). node_exporter has no
+# authentication, so the wildcard bind stays off the table; this is the
+# pairing that removes the unauthenticated observability surface on every
+# host, and both consumers are accounted for.
+#
+# MOUNTS. The container reads the host's /proc, /sys and / as /host/*
+# read-only and is pointed at them with --path.*; it writes nothing anywhere.
+
+[Unit]
+Description=Prometheus node exporter ({title} host metrics)
+After=network-online.target
+Wants=network-online.target
+
+[Container]
+ContainerName=node-exporter
+Image=docker.io/prom/node-exporter:latest
+Network=host
+PodmanArgs=--pid=host
+Exec=--path.procfs=/host/proc --path.sysfs=/host/sys --path.rootfs=/rootfs --web.listen-address=127.0.0.1:{port} --web.listen-address={lan}:{port}
+Volume=/proc:/host/proc:ro
+Volume=/sys:/host/sys:ro
+Volume=/:/rootfs:ro
+HealthCmd=wget --spider -q http://localhost:{port}/metrics
+HealthInterval=30s
+HealthTimeout=10s
+HealthRetries=3
+HealthStartPeriod=30s
+
+[Service]
+Restart=always
+RestartSec=10
+
+[Install]
+WantedBy=default.target
+"""
+
+
+def render_node_exporter_unit(inv: Inventory, host: str) -> str:
+    """The node-exporter quadlet for one host: shared template, per-host
+    title, LAN address from the hosts map, port from the scrape job."""
+    svc = inv.service("node-exporter")
+    if svc is None:
+        raise SystemExit("inventory has no node-exporter entry")
+    job = f"node-{host}"
+    port = next((str(e["target"]).rsplit(":", 1)[1] for e in svc.get("scrape", [])
+                 if e.get("job") == job), None)
+    if port is None:
+        raise SystemExit(f"node-exporter scrape declares no job {job}")
+    lan = inv.hosts[host]["address"]
+    return NODE_EXPORTER_TEMPLATE.format(host=host, title=host.capitalize(),
+                                         lan=lan, port=port)
+
+
 def check_drift(inv: Inventory) -> list[str]:
     problems: list[str] = []
     rendered = render_pihole_hosts(inv)
@@ -508,6 +593,15 @@ def check_drift(inv: Inventory) -> list[str]:
     for missing in [f for f in want if f not in have]:
         problems.append(f"inventory declares a scrape prometheus.yml lacks: {missing}")
 
+    svc = inv.service("node-exporter")
+    for host in (svc or {}).get("hosts", []):
+        for directory in inv.unit_dirs(svc, host):
+            path = REPO_ROOT / directory / "node-exporter.container"
+            if path.exists() and path.read_text() != render_node_exporter_unit(inv, host):
+                problems.append(
+                    f"{directory}/node-exporter.container is not the render of the "
+                    f"template (scripts/service-map.py render node-exporter-unit --host {host})")
+
     probes_want = sorted(set(probe_facts(inv)))
     probes_have = homepage_probes(REPO_ROOT / "shared" / "homepage" / "services.json")
     for extra in [p for p in probes_have if p not in probes_want]:
@@ -568,7 +662,8 @@ def main(argv: list[str] | None = None) -> int:
     p.add_argument("--service", required=True)
     p.add_argument("field")
     p = sub.add_parser("render")
-    p.add_argument("artifact", choices=("pihole-hosts",))
+    p.add_argument("artifact", choices=("pihole-hosts", "node-exporter-unit"))
+    p.add_argument("--host", choices=list(Hosts) if False else None)
     p = sub.add_parser("check")
     p.add_argument("names", nargs="*")
 
@@ -632,7 +727,13 @@ def main(argv: list[str] | None = None) -> int:
         values = [s.get(args.field) for s in matches if args.field in s]
         print(json.dumps(values[0] if len(values) == 1 else values))
     elif args.command == "render":
-        sys.stdout.write(render_pihole_hosts(inv))
+        if args.artifact == "pihole-hosts":
+            sys.stdout.write(render_pihole_hosts(inv))
+        else:
+            if not args.host:
+                print("render node-exporter-unit requires --host", file=sys.stderr)
+                return 2
+            sys.stdout.write(render_node_exporter_unit(inv, args.host))
     elif args.command == "check":
         problems = check(inv, args.names)
         if problems: