The agent host's vault and SilverBullet (M5.4)

deploy/agent-host sets up the vault on nisse-host (infra/tofu#77) and
SilverBullet over it: the operator writes the vault, the agents' memory/
is read-only to it, and only the operator's Caddy reaches it, which
serves vault.dongar.net to the LAN. scripts/agent-host.sh installs and
checks it from here.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01J5Utyfzw7gF7UhjRDEtjTk

deploy/agent-host/setup.sh

@@ -0,0 +1,49 @@
+#!/usr/bin/env bash
+# Set up the agent host's vault and SilverBullet (M5.4). Run as root on the
+# host, from this folder's copy (scripts/agent-host.sh install does that).
+# Safe to run again: it changes only what differs.
+set -euo pipefail
+
+here=$(cd "$(dirname "$0")" && pwd)
+
+# The only address allowed to reach SilverBullet: the operator's Caddy
+# (docker.garrett-hall.com), which serves vault.dongar.net to the LAN.
+CADDY_ADDR=192.168.6.13
+SB_PORT=3000
+SB_UID=1000  # the image's PUID/PGID: the operator's side of the vault
+
+# The vault. Its root and everything in it belong to the operator, except
+# memory/, where each agent gets a folder of its own when it moves in. memory/
+# is root's, and SilverBullet mounts it read-only besides.
+install -d -m 0755 /srv/nisse
+install -d -o "$SB_UID" -g "$SB_UID" -m 0750 /srv/nisse/silverbullet
+install -d -o "$SB_UID" -g "$SB_UID" -m 0755 /srv/nisse/vault
+install -d -o "$SB_UID" -g "$SB_UID" -m 0755 /srv/nisse/vault/infrastructure
+install -d -o root -g root -m 0755 /srv/nisse/vault/memory
+
+# SilverBullet's stack, where the docker role keeps stacks.
+install -d -m 0755 /opt/stacks/silverbullet
+install -m 0644 "$here/silverbullet/compose.yaml" /opt/stacks/silverbullet/compose.yaml
+
+# Only Caddy may reach SilverBullet's port, re-applied whenever Docker starts.
+install -m 0755 "$here/nisse-firewall" /usr/local/sbin/nisse-firewall
+cat > /etc/systemd/system/nisse-firewall.service <<EOF
+[Unit]
+Description=Only the operator's Caddy reaches SilverBullet (deploy/agent-host)
+After=docker.service
+BindsTo=docker.service
+
+[Service]
+Type=oneshot
+RemainAfterExit=yes
+ExecStart=/usr/local/sbin/nisse-firewall $CADDY_ADDR $SB_PORT
+
+[Install]
+WantedBy=docker.service
+EOF
+systemctl daemon-reload
+systemctl enable --now nisse-firewall.service
+systemctl restart nisse-firewall.service  # picks up a changed rule
+
+docker compose -f /opt/stacks/silverbullet/compose.yaml up -d
+echo "SilverBullet is up on port $SB_PORT, reachable from $CADDY_ADDR only"