Say when the systemd unit has moved on

update.sh pulls the code and restarts, and says nothing about the unit --
so a host can run a new release under the old confinement and fail in a
way that points nowhere. Dropping ProtectKernelTunables is exactly such a
change: without it applied, an agent chat cannot start a sandbox at all.

It compares the *template* against the one last applied here rather than
against the installed file. An installed unit grows host-specific lines --
an ordering dependency on whatever serves the models, a note about how the
prefix is mounted -- and diffing the files would warn about those forever.
A warning that always fires is one nobody reads.

Reinstalling automatically would clobber those same lines, so it only says
so and leaves the merge to a person.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

deploy/install.sh

@@ -110,6 +110,10 @@ sudo install -d -o "$SERVICE_USER" -g "$SERVICE_USER" -m 750 "$PREFIX/data"
 echo "== systemd unit =="
 sed -e "s|__PREFIX__|$PREFIX|g" -e "s|__SERVICE_USER__|$SERVICE_USER|g" \
     "$HERE/lembas.service" | sudo tee /etc/systemd/system/lembas.service >/dev/null
+# Which version of the template this host is running. update.sh compares
+# against it and says so when the template moves on, because the installed
+# unit usually grows host-specific lines and cannot simply be overwritten.
+sha256sum "$HERE/lembas.service" | cut -d' ' -f1 | sudo tee "$PREFIX/.unit-applied" >/dev/null
 sudo systemctl daemon-reload
 
 echo "== self-signed cert for $SITE_HOST =="