docs: reboot-tested the frank-medium trio

Rebooted dankserver unattended and verified without any manual step: all three
units active 59 s after boot, both replicas healthy ~3.5 min after boot, real
completion through :7770 — the failure mode this repo has been bitten by before
(a service that only ever ran from compose and stayed dark after a reboot).
Records why it works: [Install] WantedBy=default.target wired into the
generator's default.target wants, plus Linger=yes, plus a disk-backed compile
cache so a cold boot needs no warm-up beyond the model load.

serverAppConfigs-docs/LLM/frank-medium-radiance-mxfp4.md

@@ -199,6 +199,27 @@ the entrypoint/healthcheck/proxy scripts mounted read-only out of
 The healthcheck reads `PORT`, so one probe serves the replicas (:7771/:7772),
 the proxy (:7770) and the TP=2 target.
 
+### Boot persistence, verified by rebooting
+
+The trio was reboot-tested end to end (2026-09-16), because this repository has
+been burned before by services that ran only from `compose.yaml` and stayed dark
+after a reboot:
+
+```
+sudo reboot                 # unattended; ~2 min 14 s to graphical.target
+# ... no manual step at any point ...
+systemctl --user is-active frank-medium-a frank-medium-b frank-medium-proxy
+  -> active active active            (containers up 59 s after boot)
+curl http://127.0.0.1:7770/health   -> both replicas UP ~3.5 min after boot
+```
+
+Why it comes back: each unit's `[Install] WantedBy=default.target` — the generator
+wires all three into `default.target`'s wants (they report `generated`, which is
+the healthy state on this host's v1 quadlet generator and cannot be `enable`d) —
+plus `Linger=yes` for the deploy user, so the user manager runs without a login
+session. The replicas need no warm cache: the compile cache lives on disk
+(`/cache`) and the model loads cold in about three minutes.
+
 ## Deploy and verify
 
 ```