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/caddy/vault.dongar.net.caddy

@@ -0,0 +1,10 @@
+# The vault's SilverBullet, for the operator's Caddy on docker.garrett-hall.com
+# (/opt/stacks). HTTPS from Caddy's usual automatic certificate; LAN only.
+vault.dongar.net {
+	# Anyone outside the LAN gets nothing. Caddy still answers Let's Encrypt's
+	# checks, which it handles before the site's own routes.
+	@outside not remote_ip private_ranges
+	respond @outside 403
+
+	reverse_proxy nisse-host.garrett-hall.com:3000
+}