fix(nh3): NFS clients mount nh3-nas shares on first access; record guest power-loss expectations

After the 2026-09-24 NH3 power outage every NFS line from nh3-nas failed at
boot: nh3-docker's /mnt/compose and /mnt/backup, and nh3-dev's /mnt/backup.
The NAS is the slowest box to serve NFS, and the plain fstab mounts stayed
down until remounted by hand. nh3-dev's /mnt/smithy already used
x-systemd.automount, and the same boot shows it self-healing on its next
access. playbooks/nh3-nfs-automount.yaml brings the other lines to that
shape (_netdev,nofail,x-systemd.automount,x-systemd.mount-timeout=30).
Hard-mount semantics are unchanged; only WHEN the mount happens moves.

Applied and read back on nh3-docker and nh3-dev: every nh3-nas line carries
automount, each automount unit is active, and each share is NFS-mounted after
access. A second run on nh3-docker is a no-op. The fstab check judges only
errors the rewrite ADDS, because nh3-dev's installer cdrom line has a
pre-existing verify error. The first run caught that and aborted without
writing.

servers/nh3-pve/README.md now lists each guest's expected state after a
power loss: nh3-laser is on-demand and stays off (Prime), pbs-nh3 now has
onboot=1 (it had none and stayed down), and pfi-gx10 is bare metal that
does not auto-power-on.

playbooks/nh3-nfs-automount.yaml

@@ -0,0 +1,73 @@
+# NH3 NFS clients: mount nh3-nas shares on first access, not at boot.
+#
+# Why (2026-09-24 NH3 power outage): after a site-wide power loss every box
+# boots at once and nh3-nas is the slowest to serve NFS. Plain fstab NFS lines
+# failed at boot on nh3-docker (/mnt/compose, /mnt/backup) and nh3-dev
+# (/mnt/backup) and stayed down until someone remounted them by hand.
+# nh3-dev's /mnt/smithy already had x-systemd.automount, and the same boot
+# shows it self-healing: its first access at 1234 failed, and the next access
+# at 1309 mounted it with no intervention. This brings the other lines to that
+# shape. Hard-mount semantics are unchanged; only WHEN the mount happens moves.
+#
+#   scripts/elway infra-ops@10.100.50.40 --playbook playbooks/nh3-nfs-automount.yaml
+#   scripts/elway infra-ops@10.100.10.50 --playbook playbooks/nh3-nfs-automount.yaml
+#
+# Rerunnable: lines that already carry x-systemd.automount are left alone, and
+# the activate steps skip a path whose automount is already active.
+
+steps:
+  - name: Back up fstab
+    sudo: true
+    shell: cp -p /etc/fstab /etc/fstab.bak-20260924-automount
+    creates: /etc/fstab.bak-20260924-automount
+
+  - name: Add automount options to nh3-nas NFS lines that lack them
+    sudo: true
+    shell: |
+      set -eu
+      awk -v OFS='\t' '$1 ~ /^10\.100\.50\.50:/ && $3 ~ /^nfs/ && $4 !~ /x-systemd\.automount/ {
+             $4 = $4 ",_netdev,nofail,x-systemd.automount,x-systemd.mount-timeout=30" } { print }' \
+        /etc/fstab > /etc/fstab.automount-new
+      # Judge the rewrite by what it ADDS: nh3-dev's installer cdrom line
+      # (udf,iso9660 vs an attached iso9660) is a pre-existing verify error
+      # that has nothing to do with NFS, so "zero errors" would refuse forever.
+      errs() { findmnt --verify "$@" 2>&1 | sed -nE 's/.*[^0-9]([0-9]+) errors?,.*/\1/p' | tail -1; }
+      before=$(errs); after=$(errs --tab-file /etc/fstab.automount-new)
+      if [ "${after:-99}" -gt "${before:-0}" ]; then
+        rm /etc/fstab.automount-new; echo "rewrite adds fstab errors ($before -> $after); fstab unchanged" >&2; exit 1
+      fi
+      cat /etc/fstab.automount-new > /etc/fstab
+      rm /etc/fstab.automount-new
+      systemctl daemon-reload
+    when: "awk '$1 ~ /^10\\.100\\.50\\.50:/ && $3 ~ /^nfs/ && $4 !~ /x-systemd\\.automount/' /etc/fstab | grep -q ."
+
+  # Activate now rather than at next boot: a path that is already a plain
+  # mount cannot take an automount on top, so unmount (fails safely if busy),
+  # start the automount, then touch the path so it mounts through autofs.
+  - name: Switch /mnt/compose to automount
+    sudo: true
+    shell: umount /mnt/compose && systemctl start mnt-compose.automount && ls /mnt/compose >/dev/null
+    when: "grep -qE '\\s/mnt/compose\\s.*x-systemd.automount' /etc/fstab && ! systemctl is-active -q mnt-compose.automount"
+
+  - name: Switch /mnt/backup to automount
+    sudo: true
+    shell: umount /mnt/backup && systemctl start mnt-backup.automount && ls /mnt/backup >/dev/null
+    when: "grep -qE '\\s/mnt/backup\\s.*x-systemd.automount' /etc/fstab && ! systemctl is-active -q mnt-backup.automount"
+
+verify:
+  - name: Every nh3-nas NFS line carries x-systemd.automount
+    shell: "! awk '$1 ~ /^10\\.100\\.50\\.50:/ && $3 ~ /^nfs/ && $4 !~ /x-systemd\\.automount/' /etc/fstab | grep -q ."
+
+  - name: fstab has no parse errors
+    sudo: true
+    shell: findmnt --verify 2>&1 | grep -qE '(^|[^0-9])0 parse errors'
+
+  - name: Each automount is active and its share is mounted after access
+    shell: |
+      set -e
+      for m in $(awk '$1 ~ /^10\.100\.50\.50:/ && $3 ~ /^nfs/ {print $2}' /etc/fstab); do
+        u=$(systemd-escape -p --suffix=automount "$m")
+        systemctl is-active -q "$u"
+        ls "$m" >/dev/null
+        findmnt -n -t nfs,nfs4 "$m" >/dev/null
+      done